Do you need to upgrade your router? Most of the time the bottleneck is the ISP limits on the Internet connection, not the modem or router. If you do want to replace your router, my vote is Opnsense. You can run it on pretty much any x86 machine with at least two Ethernet ports.
If you’re not doing much computing, then the idle power consumption is much more important than the tdp, in which case the motherboard and other hardware are more important than the CPU. For your use case, something like a tinyminimicro 1L PC or a Celeron mini PC would be good. I’ve personally played around with
Most of these boxes are just Celeron or Intel i3 based computers with a few extra NICs, they’ll run pretty much anything just fine. They don’t have actual switching hardware, but they’ve got enough CPU juice to push gigabit connections with a few simple rules/filters. I have an n5105 based one with six i226 NICs, with a simple bridge it can throughput close to 2.5gbps in iperf.
I’ll check that out, thanks!