Poroton (36.5 cm) versus lightweight expanded clay aggregate solid wall (41 cm)

We are building without insulation and clinker. Inside, there will be lime-gypsum plaster. Outside, only plaster as well.

So it is a stone with which you can build. Monolithic at 36.5cm, it is okay in terms of energy standard, but no more. Sound insulation rating as well.
Don't get me wrong, I just want to relativize the statement that it is a "very good stone".
It depends on what your requirements are.
Everything else then becomes a philosophical question.

So KfW 55 with the stone is the lowest limit I would say. Although KfW55 is only conditionally meaningful. In the end, it's a back-and-forth calculation. The combination of S9 with passive house window I find interesting. Energy-wise you now have a Golf (stone) with a (Porsche). I'm not a construction professional either, sounds a bit strange to me. Sound insulation is also such a thing. The question afterwards is whether the overall concept fits and how your individual perception is. Because if the windows are no good, the wall is only conditionally decisive. On paper, the sound insulation value is not particularly good according to calculations. Yours has about 41 db. I have a filled one from another manufacturer that has 46db. Is noise an issue? Street, train or something similar?

Don't get me wrong, I just want to put the statement that this is a "very good stone" into perspective.