Preliminary floor plan of the planned house - feedback?

146 m² living space

That won't work. With a guest room, dressing room, utility room, and second (third?) bathroom, you should be thinking from 160 m². The drainage of the children's bathroom runs through your living room. In the living room, you would have to accommodate a downpipe somewhere. Look at floor plans (Google image search), have some catalogs sent to you (home builders), and check out real existing houses (friends, relatives, show homes)! Ask friends and relatives how many m² they have... At the end of the day, you could also hire an architect for the planning.

I'm just starting to work on the second draft

Sure, at the end of the day you'll probably end up at the architect BUT as I said, I would like to have an overview beforehand so that we only have to discuss minor details

Thank you very much already for your good criticism!
It has already helped me.

Then here are a few tips right away: if you want to go to a real architect, you don’t need to bring any drafts. If you want to go to a model home provider, you don’t either – they only have house "Ilse" with an extra shower in the WC anyway (usually, they don’t want the salespeople to get creative there). If you go to an engineer who has the aesthetic sense of a bulldozer, it’s good if you bring something and are informed. The same goes if you want to build according to your own plans – but that takes a lot of practice.
At least that’s our experience :D (we tried everything)

I don't want to leave it like that with the show house. We also decided on a prefabricated house provider and a type of house offered by them, but we could have changed everything inside (except for load-bearing elements) and individually designed the house with its rooms. For example, we swapped two rooms and moved a few walls on the upper floor.

I don't think I'm the first person who wants to first figure out what they want (and especially if it's feasible) :D

In the first step, I just want to get a clear idea of how much floor space I need. For me, the first draft was coherent. However, I didn't consider that the stairs lead against a wall :D

We have a few floor plans lying around here. However, there are hardly any that plan with 2 bathrooms upstairs. We were already at the prefabricated house park, but somehow there wasn't really anything there that we would have liked. That's why I got creative myself.

It probably won't be the architect who has free rein and can do as he pleases. I just know too well what I would like :D

Yes... you can move all walls in model houses, but then they usually work worse than before - especially if you want to add rooms. Floor plans with a master bathroom already exist quite a few on the internet. Good architects have a better eye and usually also know better how to implement what you express as your wishes. We also did not take an architect - just saying that the option of an independent architect is definitely a reasonable and certainly good option.