Possible to relocate home folders to another volume?

Personally, I recommend people avoid the use of the built-in home folders and just create user-specific folders on their own unless an extensive user base makes that unwieldy.  They can't have the same name as the user (including you can't just change upper/lower case), but it's easy to just create Johns_share instead of John.  This gives you far more control and also allows a user access both locally and via ReadyCloud if you give "both users" the proper access.

But if you do want to continue using them, when you EXPORT the primary volume, the remaining volume becomes the primarily one, so the home folders (but not their contents) will be migrated, and re-importing the old primary will not change that.  Any content still in the home folders on the original volume will actually still be there, it just won't be accessible. So data migration requires backup, deletion of data in the old home folders, and restoration in the new.  If you have Time Machine backups, they will be especially hard (if not impossible) to migrate data from.

This will also migrate the apps folder and is supposed to migrate the apps themselves, but I have done some experiments where that didn't happen.  If you run apps and it's an option, removing the apps and re-installing after migration of the folder is probably best, though I do have a post available on how to manually migrate them via SSH.  Since the remainder of the OS is in RAID on all volumes, that's not affected.

I am sure it is possible to migrate them via SSH as well, but I've not done it.  There are hidden files and folders as well as mounts you would need to get right.

EXPORT is accomplished via the volume gear icon.  Once that is done, each actual user folder will not be created until the user logs in (or you log in for them) or you use mkhomedir_helper via SSH.  Import is accomplished by simply installing the volume with the power off and powering up.  The OS and swap partitions will need to re-sync, but that's quick.

Note that once EXPORTED, you cannot simply re-install the old primary as a primary volume, so making a backup before you start this process is a must, just in case something goes wrong.