OpnSense is great and should be used as the firewall.
VyOS is great, but it’s more of a router software, enterprise grade while at it. It can do firewalling but it’s unnecessarily complicated compared to OpnSense.
OpenWRT is an exceptional WiFi/Wireless AP software and then can do firewalling too but shouldn’t be used as the main fw imo
Sophos may or may not be great, no experience with it on my side, and won’t be any as it’s not open source AFAIK
Mikrotik hardware may be priced fairly, sometimes, but their software and configuration thick client is just a terrible mess. It does indeed require certifications to set it up, even if you’re a well battle experienced security guy. It’s just bad imo, sorry
The alternatives you listed are not quite on par.