Wireguard adds nothing unless you'd want to terminate it on the router. In which case it adds so very little it's unnoticeable.

About any n100 will do. Question is in their reliability which mostly comes down to power regulation components quality. Not performance.

One of my installs runs on a repurposed old android phone. Which has about 100 times CPU capacity of the router I write this through, and that one being cheap tplink shit still terminates wireguard at link speed which is 100Mbps. You don't need fancy gear for routing. And you don't usually need gigabit uplink because speed is limited way upstream.

But if you want "the right gear and damn the price" go get a Microtik. They are very good.