42.5 cm aerated concrete and 400 cm wide windows and venetian blinds

I think you favor something or find it better, and then you should do it that way; whether it will also be better/faster/easier overall remains to be seen. I think a construction company can explain why they consider something sensible, and I can then decide whether I want to follow that. I do not see the advantages you mentioned in relation to the goal of having a well-inhabitable and reliably built house that is good for me, or I would weight them differently. Usually, the mess happens where you least expect it, otherwise, you could generally prevent it. It is more decisive who the acting persons are, because the best material is useless if the person handling it cannot manage it. Therefore, I at least try to use what my chosen craftsman knows well, or I change the craftsman, but as you could read, I then failed elsewhere.
We also have very large and many window surfaces, and ultimately your energy consultant will tell you which string to pull better to increase your insulation effect. Your statement about this is a bit too simplistic for me.

Thermal insulation is relative anyway

Maybe you want to receive funding, then you should not do that, or you want to insulate your house as much as possible, then the quality of insulation is already an important point. This can be changed by other windows as well as by masonry etc., and the respective shares or to what extent it is "all the same" can in turn be calculated by your energy consultant. In addition, there are many things to consider with maximally large window surfaces that can influence living quality.
If that offers you a significant advantage as an allergy sufferer, then it is already decided, although I would doubt that the stone beneath the later plaster with primer and multiple coats of wall paint or other finishes penetrates disturbingly inward. As an allergy sufferer, I would rather scrutinize this in terms of wall plaster and paint or the general use of materials indoors up to furniture fronts, light sources, etc. These you will be exposed to directly and permanently, the stone wall rather not.

Regarding sound insulation, we have no special requirements – the property is in a residential area in a forest location.

Exactly our situation, and I almost failed because of that. For example, I expected only sheep and birds as sound and then got really loud wind as a very strong noise, which occurs here in our region in abundance, which I did not know from my original region. Since we eliminated another expensive error and implemented further subsequent insulation measures, it is considerably better; I already had the issue of house sale in mind, it was that bad at the beginning with our open construction method. I should have inserted a soundproofing layer of wood fiber in the roof insulation to decouple it, but it was too late for that. Maybe it is different for you, just an info.
I read that you know exactly what you want and maybe therefore see the glass half full on the other side, which is why I would then also decide in my house for my idea. Nevertheless, it is by no means the case that on one side more crap is built than on the other; there is always some "smearing," depending on the craftsman, I would prepare myself for that at least – as I said, it always depends more on the acting persons, otherwise the decision would always be easy and your version presented here would always be the right one; that would be nice.

That means I am clear about the material properties and everything fits. Now it is about what you have to pay attention to during construction – even as a builder, it can't hurt to know what is important and not always just rely on others.

I can agree with you there.
In construction, one should ultimately pay attention to everything, but above all to the choice of the executing persons (which unfortunately worked less well for us despite much effort), because a skilled and committed craftsman will not install crap for you. As I said, as an allergy sufferer, I would especially think deeply about the directly acting things. Maybe you will present your pro

We have a house made of filled expanded clay bricks, local, 42.5 cm.
Have you heard of the Octameter for solid houses, little sawing, no botched pockets, almost no plaster cracks.
Do you really want to live in a greenhouse?
Think about the windows, 4m windows are already very heavy to open.

This thought is justified and also shows that it depends more on the consideration of one’s own needs and feelings rather than on a certain wall construction.
A visit from to us is still pending, and then I will try to convince him that living well in a greenhouse is possible. But I understand his basic statement, which is why I would rather pay attention to such effects (sun, heat, climate, air quality).

Unfortunately, reality looks like this: you repeatedly see construction defects or builders curse bad decisions, even when "professionals" were at work.

Yes, there are also Monday cars, even though many capable robots and humans work on that car.
However, you cannot call it a bad decision when you pick one thing or another and don’t get it flawless.
Problems could be, for example, unskilled craftsmen who know nothing about physical laws, material properties, etc., and then apply the material incorrectly.
Problems could also arise from an overly tight construction schedule, insufficient drying, too exotic or extravagant desired features or dimensions, and also too large span widths!, many angles, meaning poor planning, poorly prepared ground, etc. And much of this is in the builder’s control or is the cause.

You also cannot speak of construction defects when you determine for yourself that, for example, ETICS [External Thermal Insulation Composite System] is not the best choice for your house. For example, we built with ETICS but would not do that anymore (the reasons are irrelevant here). But that does not mean we have construction defects and that the monolithic neighbor is free of defects or a guarantor against facade cracks.

Even your own (half) knowledge only helps to a limited extent: you would basically have to be present during the execution. Then, with your half knowledge, you still couldn’t tell the worker anything because you have no authority to give instructions. That could ultimately have consequences that lead to construction defects. And then without warranty because you possibly botched it yourself.
If you come to the site manager with half knowledge, he has the choice of friendliness or some other reaction. In the end, your half knowledge built up over years could be based on one or more false statements or connections. What you were told 4 years ago does not necessarily hold true today.

I only have very dangerous half knowledge in a few areas and would like to change that.

A statement from you in 2021. If in the meantime, almost 4 years have passed, you have studied (self-studied) construction or learned a related trade, chapeau. But apparently not, because otherwise you wouldn’t be asking.

So it remains dangerous half knowledge.

Therefore, it must be valid that an aspiring builder informs himself as best as possible about "house construction" in a "house construction forum", right?

Of course, people inform themselves here about house construction.
But there are no mechanics, bricklayers, electricians, or architects here in the forum. They are all currently working. However, tips here can come from DIYers who install their own materials. No one here has completed a complex house construction.

You know that the forum mostly consists of builders who know what materials were installed in their house but can only talk about the "properties" of the materials used, if at all.
But ultimately, very few have stood behind the craftsmen for hours watching their fingers or asking what type of compressible tape is used or whether they are botching the construction.

I just want to understand the whole subject.

And that’s exactly what it is with the topic "house construction":
Find a good company and not just look at the bottom right price, which, the cheaper it is, could be a sign that too few trained workers are involved.
Have tenders made by an expert who understands something about it.
As a layman, it is best to ask the expert directly and not other laymen.
And much more, e.g., commission a soil investigation, don’t overstretch span widths, best not to ask suggestive questions.

… and when you have a good gut feeling, trust your contracting partner.
I know you don’t want to hear or read that.
But in my opinion, it is exactly the right approach concerning house construction.
You will—I suppose—not understand a complex house construction, and that is exactly the issue you indirectly address. The forum itself can offer you individual solutions—as individual as the user and user’s application.

You are so successful in your profession that you can afford a house. When outsiders who think they know everything come to you and want to explain your job, how do you like that? Your main task is to find professionals who can turn your heap of money into your wishes. Half knowledge on your part does no harm but should not be the standard for building error-free. PS: Control never hurts but should also be done with a [Blausachverständigen].

Thank you , I forgot him!

Blausachverständigen

Of course, it is the building expert (without L) who has the knowledge and whom you hire for yourself and let his knowledge work. Because even a

old "construction phase"

in other words the construction hare (without P), you do not become, and the knowledge of the old hare is probably no longer up to date.

Thank you for the very detailed answer!

If we go back to my original post, it was less about discussing different wall constructions – I have chosen my favorite (also in consultation with the shell builder, who has already processed everything several times) and basically just want to clarify whether the considerations regarding the roller shutter box, ring beam, and reinforcing mesh are correct – "can it be done like this? Am I overlooking something?"

Do you really want to live in a greenhouse?

Well, if you want to call it that, then I suppose I do. If you enter "glass bungalow" into Google, you get an idea of what I have in mind. Taste is subjective – but that can also be left alone.

Or you want to insulate your house as much as possible, then the quality of the insulation is indeed an important factor. This can be influenced by different windows as well as masonry, etc., the respective shares or to what extent it "doesn't matter" can be calculated for you by the energy consultant

Well, beyond a certain point, it's just physics. Even a quadruple glazing does not have anywhere near the same U-value as a 42.5 cm aerated concrete wall or one made of brick plus external thermal insulation composite system. If my main living area's walls now consist of 60% windows, the adjustment factor is quite small. Of course, if you are alluding to subsidies, you may be right. In my view, that's just a farce. Currently, I don't see that we need or would receive any funding.

Regarding wind, I have no concerns – we are building on a plot in the second row, surrounded by a forest plot and residential development – so it is windless there.

Thank you for the very detailed answer!

But you did not understand it, as I read.