Just do a search on your favorite search engine for "btrfs raid5/6 write hole bug" and you'll see. If power gets cut, any file on the set of disks could be missing, or just have bunch of garbage.
One for XFCE. A reasonble workflow with lots of customizability. Default is a Windows XP workflow, but with extensions you can emulate any desktop, including MATE. The XFCE apps are light and stable with poweruser features, while being reasonably easy to approach.
Endeavor's problem is a Calamares problem in specific.
Pro tip: use an external partition editor before the install. For endeavor, this used to be gparted, but is now partitionmanager. (It even comes with the ISO!)
they got crippled a WHILE back...