Allkauf house or keep looking / Allkauf house quality?

Hi,
my wife and I want to build a house for our (soon) two children.
We have already reserved a plot for a detached single-family house. Construction will start at the earliest in 2021, so there is enough time to get more detailed information.
A single-family house with Allkauf Haus would be possible / affordable according to our rough ideas, the option to do some of the finishing work ourselves is somewhat reassuring. We would build almost turnkey, but I might install the insulation myself during my vacation to have a buffer. Since the cost guarantee lasts for two years but expires next year (2020), we would not necessarily be tied to Allkauf Haus.
I am now interested in each trade and would like to get an impression with your help of the quality level of an Allkauf Haus and whether the compromises that come with a prefab house (especially an Allkauf Haus) are acceptable for us.
Let's start with the wall structure.
I have read on various sites that a prefab house has good thermal insulation due to the wall structure, but this construction method is said to have a negative effect on sound insulation.
Then there was a statement somewhere that you need special anchors if you want to hang heavy things on the wall… is this still the case with Allkauf Haus?
And last but not least: staining on the exterior plaster after a short time (because of the good thermal insulation)… What does “after a short time” mean?

I hope I am still in the right category “General Questions” with such specific questions, but maybe this discussion will lead us to decide against an Allkauf Haus.

Regards
Daniel

PS: maybe you also have other points that clearly speak against Allkauf Haus / against the wall structure of the company Allkauf Haus. Then I would of course be glad if I could benefit from your knowledge, thanks.

I would have expected different questions now than about insulation and plaster!

Have you dealt with what has to be carried out by the builder on site and why Allkauf Haus comes to such great "promotional prices"? That certainly is not only because of the shell construction variant?!

Allkauf Haus is actually the absolute self-build house, which doesn’t sound right to you even though they build turnkey. By the way, Allkauf Haus belongs to DFH, which also includes Massa Haus and Okal Haus.

What exactly do you mean by this:

Since the cost assurance runs for two years but already expires next year (2020), which is why we would not necessarily be bound to Allkauf Haus.

???

Does that mean you have already signed an Allkauf Haus contract? Are you sure you understood the clause about the cost assurance correctly? I think there is a mix-up here.