My understanding is that you have to have at least a one (1) disk Array, then you can have as many ZFS pools configured how you like. Remeber this is Unraid, you NEED TO HAVE an Array, even if it's only one (1) disk. ZFS RaidZx, mirrors, etc are only for pools. You can put all your data on the ZFS pool(s) you create and point Dockers (i.e. Plex) to pull the data from them instead of a traditional array, BUT you still need at least a 1 disk Array.
You can format your Array disks as ZFS, put them in the Array, but they will not be a ZFS pool of any kind. They'll just be formatted as ZFS and get a few of the ZFS attributes.
I'm still learning this ZFS file sys, so confirm what I'm telling you.
Good Luck.