Floor plan design single-family house with around 150 m²

I would consider any floor plan rubbish that only "fits" with one furniture arrangement

That’s not quite true, I can still swap furniture with my floor plan now – the piano can be replaced by a sideboard etc. They are and remain all modules, as you already mentioned. But still, you have to hold on to something – you can’t just plan anything arbitrarily that then doesn’t fit at all. We don’t have any unusual furniture, so it was okay to plan based on this. I have often seen floor plans where I wondered how you could possibly fit a sofa in or where the TV should be placed – that wouldn’t have worked for me at all. It was totally unrealistic. Of course, it looked good on paper or in a great 3D simulation. I agree with the list of cuts – it would have been sensible to experiment with different numbers/sizes of furniture and see what could come out of the floor plan. Unfortunately, I didn’t think it was a big deal that everything also fit in our 16 m² rented apartment room, so it would work in a 34 m² house room – you don’t first think about leaving things out!?

That's probably a matter of opinion. I have 2.50m of shelves in the living room, full of books, and most of them are paperbacks. And many of them I read from time to time, I wouldn’t give those away either. I don’t find the book spines that undi decorative at all. Recently, they were even called a waste paper collection that could be disposed of

I've heard that too... but I also find them wonderfully decorative! I even have to say that I always find rooms without books quite soul-less. They are certainly wonderfully modern and clean, but I'm always missing something organic.

But still, you have to hold on to something - you can't just plan anything arbitrarily that then doesn't fit.

I think one should, conversely, plan more than has to "fit": so for six things seven spots, with double for the largest one, that creates more freedom for rearranging the constellation.

What some have already advised me is to separate the room a bit with a room divider - namely between the sofa and the dining table. That would be possible with a shelf in both variants (whether the piano stays or is removed), but also sensible? If the piano stays in its place, it obviously has to be quite narrow. And presumably in both cases not so deep into the room?

What some have already advised me, to separate the room a bit with a room divider [...] That would be [...] (piano remains or will be removed) possible with a shelf,

Or the piano is placed sideways, back to back with a shelf. A shelf, a shelf (from Mrs. Berta Panislowski from Massachusetts) *LOL*

Or the piano is placed crosswise, back to back with a shelf. A shelf, a shelf (from Mrs. Berta Panislowski from Massachusetts) *LOL*

Would definitely work well too! I should try it sometime