Decision aid for choosing the construction company

Honestly, I don't understand why there is so much aggression in your post. Is this the usual tone here?

There is ab-s-o-l-u-t-e-l-y no aggression in it at all – although I and many others have shaken you more gently several times, but you simply won't get it.

However, which manufacturer supplies the brakes, transmission, injection system, etc., you have no influence on.

I have had a total of six cars, all of which have served me well to very well and none of the brochures ever stated whether the headlights for the production week were supplied by Bosch or Hella. The fact that I eventually sold the previous five all had trivial / undramatic reasons – it was never because I failed to create enough Excel lists before buying (I never do that, although I am absolutely not a spontaneous type).

Sure, however, that will probably cost them quite a bit.

Sometimes the opposite is true or at least comparable in many cases.

With the Golf, you can also choose and order all kinds of engine / equipment variants.
However, which manufacturer supplies the brakes, transmission, injection system, etc., you have absolutely no influence on.

That exactly is the question, whether one needs or wants that!?
I claim that this is not the case with wullewuu, although he is partly tangled up in all these details at the moment.

I understand very well what you mean, as well as the feeling of having "free choice" and being the master of things. Until 10 years ago, I thought exactly the same. I wanted to build everything myself, of course massively and so on and so forth. Now, 10-20 years later, I neither have the time nor the desire to do that. Just like other everyday things (car, smartphone, computer...), it should simply work and fulfill the purpose for me and the family as best as possible.
So far, I am of the opinion that this goal can also be achieved with a prefabricated house provider and I do not feel "restricted" in my choice of details at all. Whether this assumption proves true, I will hopefully see in 2021 :)

Now, 10-20 years later, I neither have the time nor the desire for it. Just like other everyday things (car, smartphone, computer...), it should simply work and fulfill the purpose for me and my family as best as possible.

I can absolutely understand that!
I think at this point it is also important to assess yourself whether you like it or if it annoys you. Everyone is different in this regard, which is why this would be an important aspect for me when choosing the house building partner. Therefore, it is often important to thoroughly examine such things alongside all these technical details.

So far, I believe I can achieve this goal with a prefabricated house provider as well and do not feel "restricted" at all in my choice of details. Hopefully, I will see in 2021 whether this assumption proves true.

I definitely think so, since there is no ONE prefabricated or solid house provider. In the end, I would be almost indifferent as to whether my house is built as a prefabricated or solid construction, as long as my desired living conditions are met.

In my experience so far, which has been somewhat theoretical, some prefab house manufacturers can indeed "build individually as you want," at least in the broadest sense. Just enough that it suffices for the majority of builders.

The question is whether it’s worth it then. We’re at the point where we originally actually wanted something pre-designed, but now realize that it really hits the budget hard if you actually customize the house to your own wishes. With underfloor heating, heat pump, decent photovoltaics, and a bit of small stuff, for example, we are more than 60,000 above the catalog price of Weberhaus. And we haven’t even talked about the typical upgrade topics like faucets, tiles, doors, etc. Yet. Plus, additional construction costs shouldn’t be underestimated as quite a lot has to be done on site. It looks similar for others. And nothing was individually planned yet. I have the feeling a bit that everywhere the upgrade is charged completely on top without removing what is being replaced. By the way, the comparison with cars is misleading since cars are always serial products. At least what a reasonably normal person can afford. And with a car, you can even play around a bit with the configurator and see where your own dreams collide with the budget. With prefab houses, you have to squeeze the price for every upgrade out of the seller.