Virt manager is the least intuitive (discounting actively antiuser crap) program I've ever dealt with. I still don't quite get it and I've used Linux exclusively for more than 5 years.
Did you use the desktop or the CLI utility?
(user group setting issue is a common hiccup)
It pretty much just automates the standard Qemu/kvm setup workflows. =3
GUI might not be as powerful, but in my experience, it's similarly non-intuitive as alternatives, such as VirtualBox / UTM (macOS) / VMware Fusion/Player.
For anything more complex (e.g. GPU passthrough) you will need to drop into manually modifying XML files.