Upgrading my home network after seven years; few quick questions

I plan on completely redoing my network and it's needed badly. With spare cash I was planning on getting the Nighthawk Tri-band AX12 12-Stream AX11000 Wi-Fi 6 (RAX200-100NAS), but concluded that I would need an access point in my two story high house (plus basement... roughly 6000sqfeet..maybe a bit less).Is the Nighthawk AX6000 (EAX80) backwards compatible? Am I not seeing the actual extender?

Also devils advocate and be stupid here, but what is the point of the LAN ports on their extenders? Sure devices that may not have WiFi, but the extender and router would still be communicating OTA. Do the extenders prioritize LAN over Wi-FI and offer a better experience?

Granted I'd probably hook everything up to a switch, and let the cameras (in the near future) and everything else run on Wi-FI, but was just curious.