With whom to plan/build a single-family house?

We wanted a solid passive house. Well, the solid builders more or less politely told us that we were a bit crazy. Then we looked at timber frame, which is quite common here, but it didn’t really appeal to us. By chance, there was an advertising sign from Wir-Leben-Haus and we ended up with solid wood.
Wood certainly not for ecological reasons. The forests don’t provide that much wood.
Ecologically, building nothing or very small and minimal is best.
Also, for ETICS the Fraunhofer Institute has research on recycling or disposal that is quite promising and ecological.
Everyone has to decide that for themselves. What’s important is that the builder suits you. As Climbee already wrote.
Stone has no problem with the slope.
Timber frames tend to result in tower building – since the basement must be concrete or stone or have a retaining wall and the house built with a 1m distance in front of it.
Solid wood is somewhat friendlier for structural engineering. We have a watertight wall on the slope and a watertight base slab. The other three basement walls are not earth-contacting and made of wood. We’ve been living in the house since February 2018. So far it works without problems – it would be a problem if it didn’t.

Fraunhofer Institute has also conducted research on the recycling or disposal of ETICS that is quite promising and ecological.

The insulation materials of ETICS are often petrochemical in "nature" – made from ingredients that would not combine naturally without industrial assistance. Whether they are truly biodegradable by the stone louse, I dare to doubt: reputable sources claim that the stone louse was just a hoax, behind the Prof. Grzimek-imitating mask stood the humorist Loriot ;-)
Furthermore, I would like to reiterate my mantra here: better to rely on the "chemistry" with the builder than to fixate on a specific building material. The head-brain is far too susceptible to brainwashing attacks by marketing psychologists, while the gut-brain is less corruptible in doubt. If there is a devil, he always argues with Excel "evidence" ;-)

The insulation materials of the ETICS are often petrochemical in "nature" – made of ingredients that wouldn’t naturally bond without industrial assistance. Whether they are really biodegradable by the stone louse is something I doubt: reputable sources claim the stone louse was just a hoax, behind the mask imitating Prof. Grzimek there was the humorist Loriot ;-)
By the way, I gladly repeat my mantra here: better to rely on the "chemistry" with the contractor than to focus on a specific building material. The head brain is far too susceptible to brainwashing attacks by marketing psychologists, the gut brain is probably less corruptible. If there is a devil, he always argues with Excel “proofs” ;-)

You mean the mealworms. Well, even if they gobble up that stuff, what about the worms then? Food for humans or hazardous waste. No, there is supposed to be a recycling plant. Whether it is already operational, I don’t know. Oh, there are so many pros and cons. Only one thing is certain. The chemistry with the construction company must fit. If it doesn’t, there will be no satisfactory result, even if a perpetual motion machine were created.

This is how our building was done as well: earth and concrete work including the floor slab by a civil engineer, wooden house on top. The precision fit was within a millimeter range and exceeded all expectations, including those of the carpenter, who didn’t have to touch the concrete at all to set the walls – except at one point, where we moved the kitchen door by another 20 cm.

Wooden house on concrete foundation works according to our experience. The companies involved had excellent communication with each other.

That sounds great!
But that is not what I mean in our case.
Take a look at the photo on p. 3 pretty far down, you can see it well there: the basement floor itself is built partly from concrete and wood.

The basement floor itself is partially made of concrete and wood

This is how our entire house is built: everything in contact with the earth is concrete, the rest is wood. So we have a concrete wall on level 0 on the hillside and two partial wooden walls on level -1 on the valley side. It is mixed as in the picture.

Ah, okay, then I misunderstood you, sorry! Then your post from the last page sounds like you are satisfied so far and would do it the same way again. :)