

Some things only get applied once you restart. Take the kernel for example. It will be used once restarted. It is safe to restart at a later time but you would still be running a older kernel at that point.
So technically the update is done but not everything is using it yet. Dnf does tell you you should restart for some things to be applied. The choice is yours to do so.
I know ZFS is not the same as raid. but for most folk it services the same purpose. ZFS is a file system with raid like functionality hence i said for a software raid option it is good. meaning using RAIDZ and not hardware RAID. And yes ZFS can do so much more then raid which is amazing.