Which smart home system is suitable for our new building?

That only causes further confusion now. If he sticks with Unifi, the management functions are available within the scope of possibilities. I do not assume that TE knows anything about routing even remotely or needs it.

I admit, I wanted to see how long we could keep this thread alive with further (follow-up) questions :p But yes, this all goes too far. @Pac666 take everything from Unifi if you can afford it and have the time to occasionally check their shop to see when the needed items are available (Unifi has had delivery difficulties for a long time, items come online from time to time and then sell out within a day). That's actually the only reason I got the eufy Doorbell, otherwise I would have taken the new G4 Doorbell Pro from Unifi. If you want to buy everything at once or Unifi overwhelms you (just watch a few YouTube videos about it, the channel spielundzeug for example should appeal to you overall), then take the Fritz stuff from AVM, which will also be sufficient for you.

One more question about the Unifi Access Point I unfortunately cannot hang the Access Point on the ceiling here I have to fall back on the In-Wall HD (with integrated switch)

I then unfortunately have to mount the Access Point behind the lowboard at the bottom Is the Access Point then so strongly shielded behind it that it no longer works properly and no longer makes sense?

Alternatively, there is the AVM 6000 that we would put on the lowboard (not so nice visually)

if I have a 16 port POE switch and only have e.g. 5 POE devices connected (rest normal LAN) does the switch still consume that much power? or does it only consume as much as is connected?

the Unifi switch lite 16 port cannot be screwed into the 19" network cabinet I would then have to put it in there

This is not meant to be harsh, but a sincere piece of advice: Use AVM and extra switches where needed - done. Then you won't drive us and especially yourself so crazy.

Your questions keep going in circles. But how about a unifi FlexHD on the cupboard?

I hadn't even considered the Flex (it already looks better than the AVM 6000)

The disadvantage of the Flex is that it doesn't have an integrated switch

May I ask how many devices you have connected to the LAN at the TV spot?

I admit I'm going in circles and a bit desperate :D

With AVM, I'm currently afraid that the WiFi might not reach the garden. (AVM has no outdoor access point)
The lowboard is right by the terrace door and the garden is 10x20m long. I also want to have enough WiFi available at the end of the garden (where we will set up a garden shed) to surf and watch videos without any problems. I'd say at least 100 Mbps should arrive there (we will get 500 Mbps fiber)

With Unifi, I possibly fear it's overkill for me and that I'll spend unnecessarily too much money (which I could put into something else)
Since I don't need most of the functions of Unifi

Disadvantage of the Flex is that it doesn't have an integrated switch

There are also Flex switches. This was already mentioned here. But maybe a double socket is enough for you.
At the TV, you will then have the best WLAN reception. ;-)

May I ask how many devices you have connected to the LAN at the TV spot?

TV, media receiver, AV receiver, Retro Pi -> four

At least 100 mb/s should arrive there (we will get 500mb fiber)

Why a 500mb line if your WLAN is only doing 100-250 anyway?