Grab an Intel N100 box, throw proxmox on it, throw an opnsense VM on it and you'll be all set.

https://www.servethehome.com/fanless-intel-n100-firewall-and...

This will run line-speed 1Gbps Internet without issues.

I ended up picking a TP-Link AXE95 (v1 hardware, from Costco) and threw it in AP mode. No issues with that as long as I statically addressed it.