I've got an OpenBSD router setup on an APU2 (https://www.pcengines.ch/apu2c4.htm). It's running dhcpd, unbound, dnscrypt-proxy, openvpn server and an openvpn client and the load averages are pretty low. Haven't bench-marked throughput properly yet as I'm still configuring PF properly.
I used these [0][1] repos as a starting point, I wrote a few helpers to update dynamic dns and a DNS ad blocklist for unbound. This replaced a pfSense install and I'm happy with it so far.