If you put drives of a different Rockstor system into one, in the Storage -> Disks screen, you should see two icons next to each disk, one of which is for importing all Pools, Shares and Snapshots on that Disk. You might want to read this documentation. Suppose your Pool is a multi disk Pool, then importing from any one drive will bring data back in the form of Pools, Shares and Snapshots that are there in the set of disks.
Matters may get complicated if you are using hardware RAID of some sort. Are you? or is the RAID controller just passing through the disks for Pool level BTRFS software RAID?
Your assumed answer for (1) seems OK to me. For (2) and (3), if you are NOT using hardware raid, then I don’t see why it won’t just work like in (1).
Also keep in mind that the process only imports data. Not users, groups and other configuration information. For that you can try the config backup/restore feature.
I have a HP MicroServer Gen8 (gave up trying to make Rockstor work in XenServer without VT-d). Weighing up pros and cons of using the onboard RAID controller (Smart Array B120i). At the moment I’m leaning towards using AHCI & JBOD rather than the hardware RAID because HP’s B series cannot expand an array, and it would lock me into using HP RAID controllers (to an extent) in future.