Narrow plot, max possibilities, single-family house with low knee wall

Therefore my assumption is that the approval authority will allow noise-producing dormers.

Oops, I thought/read that the OP had already figured that out. That was just you, right? Oh, it will be fine. I see a nice house on the property.

What does the development plan say about the maximum number of floors? We are building on a similar footprint (7.8x11.8m) and knee wall/dwarf wall height of 0.00m. In a few rooms, we have planned large dormers (almost Bauhaus style), which especially brings the entire bathroom to full room height. That should be possible for you too, if 0.5m knee wall and 50° roof pitch are not enough.

Thank you for the encouragement

Because of the long eaves sides, with 50cm room height a lot of living space/children's rooms (wardrobe and so on) is taken up. I would be interested in your idea with the dormer and how you solved the layout. Is your floor plan available here in the forum? According to the development plan, only 1 full floor is allowed. For a possible approval for a second one, all adjacent owners would have to give their written consent. Only then would an examination by the building authority be possible.

We are not necessarily convinced to build two full floors, since this would, first of all, be more expensive and secondly also take away potential storage space from the attic. The basement is a thing of its own. It is not planned, but if it becomes unavoidable (utility room and storage) we will have to address it.

Exactly here. The house must be gable-end facing the street,

The other way around would be much worse.

Take my plan from #6 and make a small deduction; so 8.5m * 12m is definitely possible, IMHO also 14m depth.

Mmh, well if it's that tight, exact dimensions would be nice. A plan with 9 x 11.5 can be quite different from 8.5 x 12. Especially on the upper floor, every centimeter counts.

The other way around would be much worse.

Maybe visually, but not in terms of usability.

Is your floor plan available here in the forum?

Yes, I have posted it here. But please don't be surprised, it is a semi-detached house and not a single-family house. However, it should be adaptable.
https://www.hausbau-forum.de/threads/Doppelhaushälfte-ca-145qm-mit-satteldach-verbesserungspotential-im-Bad.32108/

I just quickly checked on Google as well. You are building in North Rhine-Westphalia, right? The definition of a "full storey" was apparently newly regulated in 2018:
"(6) Full storeys are above-ground storeys that have a clear height of at least 2.30 m. A storey is only considered a full storey if it has the height mentioned in sentence 1 over more than three quarters of the floor area of the storey below." (§2, Building Code NRW 2018; source: recht.nrw.de)

Even with a pitched roof and dormers on the upper floor, quite a bit should be possible. However, I would definitely clarify this again. As I said, I only got it from Google.

In a few rooms we have planned large dormers (almost Bauhaus style),

Oh dear. Dormers / almost Bauhaus style??? :-( I see there https://www.hausbau-forum.de/threads/Doppelhaushälfte-ca-145qm-mit-satteldach-verbesserungspotential-im-Bad.32108/ rather OBI than Hornbach *grin*