Additional qustion: If I would remove my home router from above configuration and I would connect directly 1st M4 from second floor to the modem on attic (i dont need internet connecton on 3rd floor)...

Hello, Can I connect two M4 decos in Access point mode to my router (which already has internet connection provided by WAN port) using ethernet cables? My setup would be like below: MODEM -> WAN_PORT...