(not only have none of these companies made any effort at improvement, they’ve consistently gotten worse as time goes by – remember one comedian commenting “the bar was on the ground and y’all brought shovels”)
if you decide on Gnome, keep in mind there are two main paths to follow – stock Gnome (“as the developers intended”) and Gnome with extensions (ie. addons or plugins or mods) – extensions can do everything from minor aesthetic tweaks (Blur My Shell, Rounded Corners, Remove Rounded Corners) right on up to completely changing the behavior of the window manager (PaperWM, Pop Shell) – which side of that particular divide you end up on is purely personal preference
think it more comes down to all the layers they’re having to deal with: (soon: Cosmic DE) on top of Gnome changes on top of Pop!_OS changes on top of Ubuntu changes on top of Debian changes on top of System76 hardware …
sounds like your main limitation is attaching the drives – if you can attach them all to a single system (ex. a separate computer or a NAS case) then at least it becomes somewhat easier to access them all at once
I was thinking JBOD but Wikipedia points out the same issue you mention with RAID 0, failure of one drive can mess up the logical volume which leads to a whole host of new issues to deal with during recovery