I've been down this path before. I'd argue strongly pfSense is non-trivial and will require significant time investment for most people coming off Unifi stuff to learn the ropes, and should not be considered a serious alternative for most people. They have very different target markets and this is reflected in the software. Unifi is much closer to a "plug and play" user experience in comparison to pfSense. The customization options for pfSense are of-course fantastic.
I actually reversed this choice and am back to using the Unifi Controller again - pfSense is superb in production or more-networking-enthusiast style environments, not so nice for "average" home. I used a 5-ethernet port fan-less Intel Atom box almost identical to the one you linked for my homemade pfSense router while it was running, for that purpose it was pretty good.
Point taken. I've been running linux with iptables since 1999. I also spent a few years at Cisco doing network security stuff. So PFsense was a minimal learning curve for me.
But at the same time, I run Google WiFi points as I don't want to deal with them. :)
Opnsense forums have lots of recommendation for hardware, which is the path I went recently. I went with https://protectli.com/, which are just some rebranded hardware sold on Alibaba, but they provide support ontop of the hardware.