Floor plan design for a duplex, small plot, Bauhaus style

What do you mean by limited space? I find the house quite spacious for 2 adults. I also find the open space silly and would prefer more space especially in the attic. But that is a personal matter.

As with almost all new construction plans, I find the hallway too narrow. I would have the outer door open outward. Unfortunately, this is no longer often planned nowadays in Germany, but it definitely has its advantages.

When swapping with the storage room, I would check if it’s practical to go to the toilet first, then put on your jacket, then go out, it becomes uncomfortable in the hallway.

It looks like the dining area is practically just window space? That would be bad because the sun would always shine in your face, it gets warm quickly, and you have to be careful not to spill things, and you don’t have wall space for the furniture.

At first glance, a very nice design. I would feel comfortable there. I wouldn't change anything. If children are to move in, then leave out the mini air spaces – in this size they look like laundry chutes and also somewhat silly. They have the disadvantage that sound and drafts travel to the floors.
I am in favor of the first one.

Hmm ... left half Ground floor variant 1 and 2 ... why utility room on the ground floor if there is a basement? Ground floor variant 2 ... dining area too narrow for a properly usable dining table .. that is less than 3 m Attic in both variants ... Where is the space for clothes in the sleeping area = parents? Why in variant 2 the minimal offset of the two halves? Where should bicycles etc. be stored? For a proper approach to a TV wall, try swapping living/cooking.

Nice design. I like the roof terrace by the bedroom. That is a blessing when the children have become teenagers. On a small plot, everyone has space to be outside without getting in each other's way. The air space on the front door side is no problem in terms of noise from bottom to top, since the windbreak has a door. (The noise just goes through the open stairwell) Whether you want to hear everything exactly happening at the front door is a matter of taste. Will the front have a window strip in full height similar to the air space? That could be an absolute highlight in combination with a hanging sculpture. Of course, the air space is ultimately an expensive luxury without utility. Definitely close the garden-side air space and enlarge the room on the 1st floor. I would rather design the kitchen island as a peninsula.

I summarize: 1) we are talking about a completely different object and also project than in 2019. 2) I at least overlooked, a. whether you want to move into house L or house R and b. where the profile of the co-builders/buyers/tenants (?) of the other half would be. 3) House L is 80 cm higher than house R. 4) otherwise both houses are substantially, but not completely mirror-image identical. Many "modules" of the floor plans are the same in both houses. Through this runs a common thread of planning in plenty of botched-work pockets. 5) Variant 1 only has the height offset, in variant 2 the halves are also shifted against each other in depth (three eighth meters). 6) in variant 2 house L also recesses behind the carport, in variant 1 it does not. 7) in variant 1 both halves have equally sized children's rooms, in variant 2 those of house L are significantly larger. 8) the roof terrace of house L is only much larger in variant 1 and very much larger in variant 2.

Without further explanations, much of this is still not quite clear. Overall, the design (not only because of the air spaces) appears very much like it fell out of a time machine, I have seen similar things in large numbers forty years ago. Both design variants raise the question of what kind of special treatment regarding the access roads is being anticipated here: the parking situation only really works under the (questionably approved) conditions of almost completely adjacent crossing possibilities as well as an access road in the curve. Given the general trend to approve 1x 2.50 m per house (and access roads in curves are regularly not approved at all), I mark both with big question marks.