Computer cables and Wi-Fi router

mainly my question would be regarding the access points where you would recommend them?

Somewhere behind cabinets/sideboards, etc., not near living areas/bedrooms.

If you want to be on the safe side, then simply one per floor... (but I consider that exaggerated in a single-family house)

Why deliberately shield them by placing them behind cabinets? I would install them as centrally and as high and unobstructed as possible.

We are currently dealing with exactly this issue as well. We will have an antenna on the wall/ceiling on each of the two floors, which will be connected via POE. In the basement, there will be a cabinet with a patch panel and the 24-port switch, which will handle DHCP, POE supply, as well as the control of the VLANS. There are at least 2 LAN connections in each room. Additionally, a firewall will be placed between the [Unitymediabox] and the switch. The goal is that only the components that are supposed to communicate with each other actually do, and that only the components that need an internet connection have one. We are still in shell construction, but at least the IP address concept as well as the basis of the documentation are already established.

I don't think you really need that many APs. You can install the outlets, but I would first try it with the Fritz box on the ground floor and one access point centrally in the attic or ground floor, depending on where it is needed more.

Are 100m of the cable enough?

Why deliberately shield them by placing them behind cabinets?

Because in a single-family house it is completely irrelevant... a high-frequency signal like WLAN simply cannot be blocked by cabinets (unless the cabinets are made of metal).

Even the intermediate ceilings made of reinforced concrete do not attenuate the signals so much that you no longer have reception above/below.

And yes exactly... routers and access points are really design highlights often with 1-2 cables needed for operation... yes, you definitely want to place them somewhere where they are particularly visible.

yes, often you don’t need more than one access point... but many are afraid that the desired WLAN might then not be strong enough to surf the internet upstairs sitting on the satellite dish. That is why I also wrote simply one access point per floor.

Because in a single-family house it is completely irrelevant... a high-frequency signal, which WLAN simply is, cannot be stopped by cabinets (unless the cabinets are made of metal).

Even the intermediate ceilings made of reinforced concrete do not dampen the signals so much that there is no reception above/below them.

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Sorry, that is nonsense. Especially a high-frequency signal is attenuated by pretty much everything in its path, and nothing passes through a reinforced concrete ceiling. Maybe a weak signal comes through reflections via the stairwell, but then it can no longer be used with a proper data rate.