Land planning / floor plan planning

I would want KFW40+ – simply because I think that in the long run it probably can't be wrong. The wall structure and building material are "whatever" to me, which is probably because I don't understand the differences. So I need to inform myself much more.

Fight early the madness of having to outsmart yourself half to death as a builder. There are millions of happy people in houses built entirely without being corrupted by funding programs. In your own heart, you will find a sufficient number of desires that can make building quite complicated.

Phew... you ask questions that I cannot answer due to lack of knowledge, and when I announce to build knowledge, then that is also not necessary - you are wearing me down ;) - Just kidding!

I will understand that as "focusing on the essentials that are important to oneself"

Correct, only you can express your wishes, e.g. low energy consumption, quiet like a house by the highway, floor-to-ceiling windows in the bedroom for looking inside, morning sun to wake up to, a light-flooded all-purpose room with a view of the garden and not of the neighbor's house/garage, etc.

do you see the bed you just say it simply and have special dimensions. Often 180x200 or 200x200 is drawn. Had already seen 160x200. Suddenly from looks great to a mess doesn’t fit. Honey we need furniture

You don’t need to go too deep. You want underfloor heating so the provider with air-to-air heat pump is out.
It’s a puzzle. Preferences, references, price, gut feeling.
We wanted stone on stone, passive house, ready to move in. Except for stone on stone it worked. In the meantime we moved away from the passive house as well. At some point you reorganize and decide. For us the deciding factor was not the wall construction, not the energy standard, but the sales advisor who miscalculated and wanted to pressure us through the financial broker to finance 2 rooms further.

I understand that as "focusing on what is essential and important to oneself"

Yes, otherwise you drown in "you absolutely need to know this too" stuff and end up building your energy advisor’s dream house. And it never stops: once you finally know what the very best heating system is and plan your house with the test winner interior walls, then it continues with extractor hoods, shower heads, recessed spotlights, and the like; sliding door rollers are an unexpectedly vast world of their own and yes, of course, motion detectors can also be wired with Cat7 ... ... ...

I would want KFW40+ already – simply because I think that in the long run it probably can’t be wrong. The wall structure and building materials are "whatever" to me, which is probably because I don’t understand the differences. So I definitely need to inform myself much more. Can you recommend good literature for a prospective builder? I’m willing to deal intensively with the subject – but it doesn’t have to be a degree course.

We also started out with the 40+ thing. Then we opened up and ended up with a general contractor from the region who initially planned for KfW55. At the last appointment, we asked rather formally where the extra cost for a 40+ house would be, and with the photovoltaics there’s obviously so much bonus that it now works out with a bit more insulation under the slab. So we are now where we wanted to be at the beginning but without wanting it in between ;) As for literature, I can recommend the books on the topic of building descriptions from Stiftung Warentest and the consumer centers. They include the usual traps and "savings measures" of construction companies. Otherwise, dig deep through the forum once and don’t get frustrated at the 5th thread about Ytong versus brick.