Semi-detached house - Which one is the best? Who has experience with that?

Partition wall yes, of course double-layered

Between the residential units this is no problem. Then the floor slab just has to be executed continuously with a separation joint (meaning 2 separate floor slabs). The problem I was talking about is structure-borne noise within a residential unit. This becomes even worse if it is built not as solid but as a timber frame construction; keyword flanking components. Although for 2 semi-detached houses with this special construction method I would seriously question the budget.

Isn't that possible with concrete as well?

The usual readiness-for-cover test by CM measurement is out. To my knowledge, there are also no guidelines for the readiness-for-cover test of concrete substrates. A mnemonic between screed and concrete drying cannot be established either, as the drying processes are completely different. Resistance measurement is out, since the reinforcement massively distorts the result. A capacitive measurement method might still be possible (probably rather inaccurate) and a destructive material test, where the test specimens must be taken out dry.