MrMotofy

LAN traffic not WAN. So yes your internet is limiting but ONLY to the internet. Otherwise a workstation to a NAS/server could be up to 10x faster

You can tell by the IP address range if they're on the same network, normally. If device behind router B can successfully ping device on router A then you're on the same

Router 2 should be a switch unless you need the extra stuff for something. At a minimum it should be in AP mode. Otherwise it's very unlikely you're getting "collisions", it's just humming along like networks do

You're planning it incorrectly. Generally ALL jacks need a single run back to the basementUUtilities/Comms area of home where the large main switch is. The internet feed should also enter and terminate there. Then devices are connected or patched to wherever in the home you need.

Wiring 1 room to another is the wrong way to do it.

DON'T use network cable splitters, use at minimum a Gigabit switch with enough ports to do what you need, ideally with extras

Many, I included prefer to run router on dedicated hardware to keep everything up and running rather than taking down the whole network for changes updates errors etc

Can't realistically compare a new product line to a used older tech...they're just not comparable in price never will be

Ask around or rent the SDS hammer drill for quick easy work of it. If you need a channel can use an angle grinder with a masonry blade. Use a small pressure sprayer of some sort with water to keep dust down. Use a shopvac and assistant too for the dust. Then with a couple 1" or water deep cuts horizontal use a chisel bit in the hammer drill to chip it out.

You can also use a regular circular saw with masonry blade for horizontal cuts. I've fount it easier to cut say 1" deep to get your quick line and make it straight to start then cut full depth as needed and blade will follow first cut. Again light water spray helps. Concrete patch can fill it then a little paint an nobody will ever know.

On inside use angle grinder to cut rectangle for a box at the location. Then chip out, a 3/4" concrete chisel can do detailed work.

Or run conduit on outside. The exterior grey pvc can be scuffed and painted to match exterior.

There's also lots of different trim options with a groove in back or hollow to run cables.I always suggest 3 cables to every normal location with 5 or so at a tv/media location.

One may be able to run through ceiling/attic area or a basement.

There's lot's of info here and in pinned comments.

Home Networking Basics https://www.youtube.com/watch?v=fjRKID2ucPY&list=PLqkmlrpDHy5M8Kx7zDxsSAWetAcHWtWFl

Outdoor Conduit HowTo https://www.youtube.com/watch?v=6vmX-hona2o&list=PLqkmlrpDHy5M8Kx7zDxsSAWetAcHWtWFl&index=2

The Unifi system requires a controller. Either a cloudkey, a Dream Machine type device OR the controller software running on a device on the network. But it technically only needs to run for setup or datalogging. Then can be turned off if desired.

All mine are older but Asus have traditionally been decent. I personally have switched over to using a custom router for none options and capability and a WAP (Wi-Fi Access Point) like Unifi. The WAP tends to be cheaper and generally all one needs to upgrade.

If you're looking for a router specifically a mini pc or open router box can make it easy. Like Protectli Quotom etc. Then run OpnSense on it and will be the last router software you need to learn. Consumer grade stuff is generally mediocre and prices have gotten a bit ridiculous.

If you think you might want multigig LAN ports in the future look for one with the ports or a Thin Client/miniPC/SFF with expansion port and add a NIC to suit your needs.

You want any 2nd or 3rd routers in an AP mode or just use a WAP (Wi-Fi Access Point)

This may help clarify a bit of the mystery of networking Home Networking Basics https://www.youtube.com/watch?v=fjRKID2ucPY&list=PLqkmlrpDHy5M8Kx7zDxsSAWetAcHWtWFl

Run fiber to uplink, then remote buildings etc have a switch and connect your indoor or outdoor WAP's

You'd probably have a simpler time by setting up Tailscale on your router and connect to that remotely. It will propagate random networks much easier