Which smart home system to choose for a flat: reed switch, detectors, camera, LTE?

What would currently be best to base a very simple smart system on in a flat (must be wireless)?
Nothing big, basically one reed switch on the door, 2 flood detectors, 1 indoor camera, maybe one motion sensor, 2 smart sockets and 2 light switches. Maybe an additional temperature/humidity sensor. And that's it.

Optionally, it would be nice if the gateway also had battery power (as there will be no mains power) and LTE in addition to wifi/lan.

I was thinking of basing the whole thing on Tapo, but there are probably better solutions?