Pretty much every BSD and Linux offers OpenSSH and OpenSSL. OpenBSD security runs much much deeper than that. The team does complete security audits of the base system and much of what’s in a default install. That is non trivial. Yes, pf has been pulled into all the other BSDs: that is the biggest assest (to me) of the BSDs. Not afraid to share quality code. OpenBSD will always be ahead on PF because it’s theirs. Others have diverged because of system design (the way the kernel networking stack is implemented, locking for SMP to name a couple) so the rule syntax may be a version or two behind OpenBSD.
If it’s a 32 bit machine you want to use, you cannot use TrueOS or DragonflyBSD. You could use plain FreeBSD, but to me, unless you are trying to compare how the same OS runs on different hardware, I just don’t see the point. Too many people come in saying “I heard this runs on crappy old hardware, well, it does but it sucks”. That’s not the fault of the OS, that’s a user fault in their own expectations.
OpenBSD can take that crappy old hardware and turn it into a decent home network firewall for typical broadband connection speeds (100Mbps or less). Better hardware and the right hardware you can easily approach or equal commercial offerings for routers and firewalls.