@TP-Link would I have to change both Decos to Access point mode? Any other setting I need to change? Don't forget that both Decos are connected to ground floor modem via Ethernet and have no direct...

I have a modem (non TP-Link) offering WiFi on the ground floor. I have two Deco M4 AC1200 connected to it via Ethernet. One is in the basement. One in the first floor. So there is no RF connection...