Thank you very much for the numerous opinions.
The essence that emerges is that there is indeed a lot of hallway space for the area. On the one hand, that is nice, open, and special; on the other hand, it is inefficient in terms of space utilization. I will sleep on it a few more nights and also show this thread to my husband. He already said to me today, "I think the design has spoiled me. I WANT this house." ;)
I can certainly appreciate some of the criticism points. The idea of having the bathroom and the office a bit larger appeals to me as well. We might even scrap the guest room entirely. I would also like to see a floor plan from the architect of our other favorite that covers our wishes. Surely someone will come up with something with less hallway.
The "huge" floor plan here is well thought out in many places but really generous, I admit that. I would not conventionally heat the garage. Maybe this hobby room, if that is even possible; the rest is simply garage/workshop/storage shed, and I would not expect that to be heated.
Some things that were criticized were explicitly requested by us, as described in the initial post. The hobby basement without windows serves the collection of retro games, which are UV-sensitive. It will really be a "cave." For space reasons, this cannot be combined with the office. These things need to be presented. The kitchen is compact — yes — but I have a 10 m² symmetrical pantry. I can already see how I will set it up and what will go in there. In the kitchen in the living area, I would only store things that we need several times a week. That is more than enough for that. I would only wish for the living/dining area to be slightly larger. I find that too much free space in rooms makes them feel uncomfortable, but that is a matter of taste. I had looked at this adapted design from someone where the living room was stretched lengthwise. Then the sofa is further away from the TV; what is that supposed to achieve?
At first glance, the design was not what I had imagined — we had rather thought of about 170m² of area. But the generous hallway in the basement already had a wow effect. I find it impressive how few walls the entire floor has towards the living side. Except for the structural pillar, everything is open. I could imagine that this would have an enormous effect.
I will let your feedback sink in.