Eaves height 3m: Does that mean a 1.5-storey single-family house is possible?

I can't understand your criticism of the development plan. The city planners don't want a knee wall here, and there are certainly many prefab houses that easily meet the specifications of the development plan

Unfortunately, the development plan is also fixed on a gable roof, which means the usual bungalows are not possible either. That is something to wonder about...

if 400, then I would build a maximum of 100 of them, so a slab of 11 by 9, no bigger, for aesthetic reasons

That is also our consideration. Did I write 'single-family house' at the beginning? Children's rooms are no longer necessary. Therefore, the little house should rather remain small. The main thing is space for a large eat-in kitchen and two toilets.

Again to the experts: Is the eaves height measured at the upper edge of the roof, not at the bottom where the wall and roof meet? You can find both versions on the internet, but the upper edge variant is in the majority.

which should be sufficient for a proper double garage

What is a garage? Our little car is used to parking outdoors. Maybe we'll treat it to a carport, a small one ...

Unfortunately, the development plan is also fixed on a gable roof, which means the usual bungalows are not possible either. One can really wonder about that ...

It's sad that some only know bungalows or town villas with hip roofs, equating a gable roof with a family single-family home.

I strongly advise just to open your eyes on the streets of the city [emoji2]

Best regards in brief

Again to the experts: Eaves height is measured at the top edge of the roof, not at the bottom where wall and roof meet?

I don't know how much the state building codes differ in this regard. It is measured at the top side, and as far as I know usually at the imaginary line where the roof extends beyond the outer edge of the exterior wall (otherwise one could cheat with the roof overhang). So theoretically as if the rain would run down the house wall from the roof.

According to the description of the requirements, the house from Nordlys could be a good inspiration for you (currently appearing repeatedly in the house pictures thread in recent weeks).

a gable roof equated with a family single-family house

Ok, you won
When leafing through various catalogs again, I actually find individual bungalows with gable roofs!

From memory, I can recommend Danwood for inspiration, not only bungalows, but also the other houses

Best regards in brief