I’m using a ~30 USD thin client with a 4 port networking card (~20 USD), just using plain nftables
on Debian. It routes handles my network just fine (complex rule set with many subnets & rules, 250/100 Mbps connection). Also using codel/cake for traffic shaping, avoiding lousy ping times even when downloading/streaming et c.
I use two TP-Link EAP 245v3 (ancient by now, but I can still use all my WAN speed from all rooms) for WiFi. Works great.
If I would redo it I’d use VyOS, OpenWRT or maybe OPNSense, but still using x86 hardware due to cost/power usage/performance. And then newer ceiling access points.
servethehome.com has a series about these fanless, multi-gigabit firewall for a while, might be interesting if you have a 200-300 USD budget?
https://www.servethehome.com/tag/firewall/
I’ve used a very similar setup in the past (J1900 CPU, 4x1 Gbps network ports) and I only replaced it due to reasons. Not noticed any performance bottle necks with that setup.
The latest N100/N200/N300/N305 CPUs from Intel looks really interesting, similar performance as my workstation but at a 10th of the power usage. N305 also has 8 cores in a passively cooled case, amazing stuff!