Which sensors for what? Inspiration

Besides some additional features like timers, which are not included in the regular glass switch, the main difference is the selection of rooms. So there is an extra menu level to choose rooms and access functions like lighting or shading room by room. This is probably also the idea to hang one of these at a central location on each floor. It is basically the light version of a tablet/display as a central control unit.

Do you need something like that? Or how have you solved such things?

Do you have a server for visualization (e.g. X1, HomeServer, Smart Visu, etc...)? These usually have the functions as well.

We are using a Facilityserver. We also have another one and an X1 running in other family properties. I would have preferred to choose something else for our new home. My wife knows the Gira Visu and wanted that too... it doesn't require an additional app then. Gira (Homeserver or Facilityserver) is outdated hardware for the price. You can get it cheaper, smaller, and more efficient... With Gira, however, a lot is already pre-made. Visu is just one of the things the server does. More important is the logic (when it goes beyond the logic of the individual components).

So far, a server was not planned. However, I saw that MDT offers a fairly affordable logic unit. Does anyone know it, is it any good?

And again about the switches. In which rooms do smart switches make sense from your point of view, or where are 2-/4-/-switches sufficient? Guest WC, utility room, technology and hallways don't need any at all in my understanding, right?

As few switches as possible and as many as absolutely necessary
What works for one may not work for you.
Please create a room book and think about how you want to control what. Then the question about the switches will also be resolved.

We don't have any switches in the utility room. Only BM.
Switch with bus coupler in the technical room. Corridors only BM.
I think we have 5 switches in the house + a few Gira G1.