Decision aid for choosing the construction company

An advantage of regional providers can be that they may be more flexible, you don't co-finance their advertising, and you are not just a small client. And that they know the local conditions.

@TE, try to untangle the knot in your head that it has to be a prefabricated house; otherwise, the discussion here makes little sense, as you yourself have already realized, although you attributed it to a different cause ("the others don't understand you"). Rather, it seems to be you, who instead of finally visiting a builder in the neighboring village, here asks multiple times what is better about it. Well, if you are of the opinion and remain so that nothing beats a prefabricated house, then just build that way, but then the discussion here is pointless. You were even given suggestions to google (!)... just check out new development areas and read the signs posted there. The assumption that only your chosen ones are appealing and build "high-quality" (the request for clarification on this is, I believe, still unanswered) is an interesting one... how do you come up with that? I also consider the statement "probably you can't go very wrong with any of the companies" at least daring. Just take the advice here.

Regarding 1.

Yes, you are right - of course the question also arises as to what percentage of WDVS houses are on the market. I doubt that this is an option for the OP... For that, one would first have to get much more involved, inform oneself, and compare. So it remains clearly in this area monolithic, and thus my assumption is simply 98% correct - as I said, nowadays either brick or Ytong is used if a solid house is built. Besides, you are also in a completely different cost range with WDVS...

2.
Yes, that’s what I want to say? Of course, a photovoltaic system pays off IMMEDIATELY energetically and environmentally, but NOT in terms of acquisition costs. So I might possibly install the system 5 years later at a lower purchase price and possibly with new energy standards? Thus, the consideration currently is, in such a phase where the price/performance ratio of photovoltaics is at rock bottom, to save/invest/spend the money elsewhere.

So if you speak in such absolute categories, your facts should also be correct. Please provide a source for the 98%.
But you are definitely wrong with 98%. Unfortunately, I have no sources; I do not know any general contractors in my area who build monolithically massive. (Here, however, presumably around 50-80% are built with clinker)

And that is also absolutely wrong. Of course a photovoltaic system DOES NOT pay off environmentally IMMEDIATELY. The energy consumed for the production is immense. That is simply nonsense.

And that is absolutely wrong as well. Of course, a photovoltaic system does NOT pay off environmentally IMMEDIATELY. The energy consumed for production is immense. That is simply nonsense.