How is the support? I would like to use CARP/pf if possible on RPI4/5.

I only have a 3B but everything I need works for me. I don’t do anything advanced with the GPIO pins, just as a headless little arm server running stuff in jails. Everything is quick. Ethernet only but network performance seems solid. Honestly feels as responsive as my amd64 desktop with 32 gb of ddr4 ram and 8 cores. My desktop has worst support for FreeBSD. No networking or graphics out of the box and significantly more work to get that “working” compared to the pi.