I would say it feels closest to steam os. It’s immutable. So make sure you understand what that is. I do like the built in wallpaper engine support. Had a bit of trouble with multi disk support. But got there after a bit of fstab tweaking.

I just installed it last night on my amd cpu/gpu rig. I can not get gaming mode working out of the box. It locks up and reboots. Their GitHub has an open issue with someone else having the same issue. Other than that, Straight forward gnome fedora setup. Install was quick. Hopefully I can figure out gaming mode.

No. Jellyfin accounts are local. So you need to set them up on the server. No external auth system