"Yesterday I disnt know what APs were, didnt know about powerlines, extender...now I know."
OP, You are on the right path.
a) Forget the "consumer router" junk, it is neither a good router or a wifi device.
b) keep reading and learning , routers _connect_ networks (likes your network(s) with internet), wifi devices (access points ,etc) allow things which are too small/mobile/stupid to have real network connection to connect to your network. Wifi router is like refrigerator frying pan, WTF is that?
c) Get a real router or build one with something like pfsense. you will learn a lot, it will give you way more than anything you can ever buy in the store on the consumer side. I run pfsense for few years and then went for Miktorik hardware ($60 for 750Gr3), Edgerouters were also mentioned if you want to stay with ubiquiti, any other major equipment manufacturer builds routers.
d) Get one or few access points , I use and like Unifi line but there are others if you don't want UniFi.
e) if you can (i.e. if you own the place), bite the bullet and run the wire. I repeat run the wire. it is simple, relatively cheap, done once , and will be 1000% better than any hack solutions of powerline or eithernet over coax. any wire would be better than Wifi. Wifi is a shared bandwidth interference prone convenience tech for (very) mobile devices. again - run the wire.
Buy once, cry once, and enjoy it for the long run vs some junk off the online or retail shelf selling you AC 9999X device.