One of the adapters always remains with the router and is connected to it via an Ethernet/RJ45 cable. The data traffic of the other adapters distributed in the house runs via this central adapter.
After setting up the Devolo Mesh System, the WLAN is deactivated on the router (prevents interference with the Mesh WLAN). This way, the wireless devices always use the optimal access point.
I myself use 5 Devolo adapters, one at the router and the others distributed throughout the house, including the basement. Works great!
Do you mean routers with the question "what fits best"? If so: In principle, any router (including those from the provider itself) with an eth (Ethernet) RJ45 connection... LG