It's a much simpler system, (and I like arch). Instead of aur you have ports, which is the same system that powers the pkg system (pacman equivalent).

SystemD is no where to be seen. Much configuration can be specified in a few simple startup files. Jails offer in built container functionality. Bhyve does virt. Zfs is native. A fresh install uses about 100mb of ram.

New releases have detailed engineering release timeliness and processes, and release notes.

There's a great handbook (though arch wiki is probably better. Brittanica vs Wikipedia sort of thing)