I know a lot of people here use pfsense on Raspberry Pi kit for some reason, but I have no knowledge or understanding of why. However!
Unless I am mistaken it not possible on RPi to run pfsence as far I know. It much more likely to be something like OpenWRT.
Pretty sure pfSense solely runs on x86-64/AMD64 on third party kit. So plenty of low power cheap Atom based mobo's for example.
Although there are also a couple of Netgate factory boxes using ARMv7 and ARMv8 based processors - this is as far as it goes. So although Pi's run ARM - there is no either official or unofficial support, compilation or porting of pfSense for the Pi family.
https://docs.netgate.com/pfsense/en/latest/hardware/...
From what I've read some folks have ported (unofficial development releases) of OPNsense to the ARM architecture. That's about as close as it gets.
@smouty is the resident expert on OPNsense related matters so he no doubt knows way more.
So yeah as you say its basically OpenWRT