Floor plan of a single-family house measuring 14x14 meters with limited ridge height

Please be concrete and say what suddenly is questionable about the wall construction?

I do not know every wall of every manufacturer, but with these walls my first question would be the sound insulation.

Sandwich roof - ..., but it is a compromise

You are already saying that yourself. Whoever orders a factory hall, gets a factory hall. The interior finishing is probably disproportionately high-quality compared to the shell construction in the end. That is like putting a Ferrari engine in a Dacia. Answer the questions! Who is the construction partner for the shell? Does he not offer any architectural services as well? Who is supposed to sign the building application for you? For which house size/design are there already many offers? Who confirmed the prices here in the forum and how many years ago?

Yes, I know, the roofs are subject to temperature fluctuations due to sun exposure and then crack, they also drum in the rain. We are risking the life test to see if a large-scale solar surface over the roof somewhat mitigates these aspects, and will gladly report

Tip: Search function. There are a few here who have similar roofs (and are actually all dissatisfied).

The interior finish is probably disproportionately high-quality compared to the shell construction in the end. It's like putting a Ferrari engine into a Dacia.

I always find it quite interesting what kind of houses architects build for themselves and which materials they use. Sometimes very creative approaches emerge that don’t necessarily have to be more expensive than the standard.
With a bit of creativity, you can also get rid of the industrial look of sandwich panels, as you can see in image searches under "kingspan single-family house."
Of course, with the large glass surfaces, it’s no longer a Dacia, and how well it performs acoustically in practice is another matter.

The interior finishing probably differs little from others.

You may be missing the experience of life in other countries to imagine "outside the German box". Hardly anyone here can imagine that water pipes can be installed visibly. In other countries, that is totally normal. That is just a small example. Those who are not bothered by such things can achieve a lot of cost-effectiveness also in the interior. Sure, there are requirements and standards, but ultimately you can do pretty much whatever you want in many places in a private house. Those who don't care about what "people" usually do in Germany have a different decision horizon.

The interior finishing is probably disproportionately high quality compared to the shell construction in the end. It's like putting a Ferrari engine into a Dacia.

Such a thing is called a "sleeper" and is a pretty cool thing for some. I love my "sleeper" (everything properly registered and never used in stupid "races"). By the way, the example is very good because in terms of body quality the Dacia is probably not inferior to the Ferrari when it comes to the core values of durability.

Tip: search function. There are a few here with a similar roof (and basically all are dissatisfied).

Good tip! About the floor plan: It is not at all my style, as I am a light and view junkie. I find the idea of equipping the hallway, which appears too large on the floor plan, as a "closet room" with a lot of storage space, a good idea. In my view, this does not work in the "dressing room". With 2 rows of closets you will practically only be bringing clothes in and out, but you will not change clothes there, let alone dress, since the freedom of movement is quite limited. Regarding a dressing room, my thought is: either do it properly or don't do it at all. I find the children's room pleasantly generously sized, but rather "put aside". Not optimal for children, but from puberty onwards it is seen as an advantage.

Regarding the floor plan:

I take this as a quote template because the OP is asking about it:
I consider 14x14 (without light well) to be a completely wrong approach. Additionally, there is an open space that is not planned accordingly to bring light into the darkness. In this respect, nothing fits to be commented on (at least not by me).

Answer the questions! Who is the construction partner for the shell construction? Doesn’t he offer any architectural services as well? Who is supposed to sign the building application for you? For what house size / design are the many offers already available? Who confirmed the prices here in the forum and how many years ago?

Names are not allowed to be mentioned here. Has been building for >10 years and there are already about 50 similar houses. Architectural service is included, but I just wanted to get some opinions and suggestions about the floor plan in advance. It is quite possible that the architect will come up with a completely different design. All offers are based on the first own design, although the exterior dimensions will not change much. Prices have all been obtained in the last 3 months. Yes, that is also all included in the architect’s contract, but we still get our own offers from the region and then choose the most suitable option. The experiences of acquaintances from the prefabricated house sector support the finding that there is quite a large margin regarding trade costs here.

I will take this as a quote template because the OP asks for it:
I consider 14x14 (without light court) to be a completely wrong approach. In addition, there is an air space that is accordingly not planned to bring light into the dark. Therefore, nothing fits here to be commented on (at least not by me)

Usually, the provider’s houses are also built with a light court, but that would have exceeded the ridge height even at 12x12 m. I had already experimented a lot with that, but I see no good geometric solution for it. One could at most install skylights facing north and leave out the gallery ceiling above the hallway or keep the children’s room and the study also open. Then there would be very high ceilings each time, ranging from about 3 m up to 5 m in height.