@BmeBenji My personal experience with Bazzite is very limited. I set it up for a couple friends and the old installer allowed you to have the home partition on a separate disk and it would "just work" (if you know the mount points in advance).
The new installer is very dumbed down in that regard. You can only choose the disks you want to use and… that's it. If you do that, however, it creates a btrfs RAID with all the disks you selected, but it doesn't indicate it will do so.
There is a partition editor, but it does not allow you to format partitions with btrfs or specify btrfs subvolumes and their mount points for the installed system, like you could with the old installer. And Bazzite has a hard requirement on btrfs.
Having your home directory on a separate disk isn't that uncommon of a setup to have, so it's just weird the installer doesn't allow you to do this at all.