Are performance phases 1-3 with the architect and lump sum offer somehow disadvantageous?

Congratulations to you. I would have just liked to get the maximum out of the house and not move any walls in floor plans that don’t really fit. If that’s enough for you, you can do all that yourself, excellent! Obviously, there still seem to be companies that provide planning services for free (or maybe you just can’t calculate). Besides, I lack the imagination of how much space a staircase needs and I’m not in the mood to google it only to end up with something that doesn’t fit.

I also laugh my head off every time people who have no clue about KNX pay me a lot of money for it. They could all do it themselves. All incompetents, original incompetents :rolleyes:

There are thousands of floor plans on the internet

But the internet does not build houses, and the floor plans there are only available as ideas, at most "dimensioned" but no more. A floor plan from the internet is only useful for the self-planner who is looking for a plan exclusively for the building application – because you cannot build from it yet. Complications are preprogrammed.