The drawing is a simplified sketch for basic home networking & fundamental to build a full speed multi storey building network.

For your situation, the benefits are:
1) Your can put RG router at suitable storey depends on your choice.


2) Only need 2 APs, each one locate at non RG router level.

3) Your internet speed is 500Mbps for 3 or more storey because the wall socket extend your router full speed LAN port either 1Gbe or 2.5G to AP. In easy word is the cable carry & connect your 500Mbps internet speed direct to your AP. No one tell you right?