You're here, that's a good start...
I tend to look at a project's Issues tracker, that gives me a feel for how the author(s) deal with feedback... some projects have hundreds of open tickets with barely any interactions, yet code updates "2 days ago".
Being here and reading about who's using what will help remove the major outliers
All opensource needs more eyeballs, which is still the advantage over closed source.
I built my own NAS from Arch (btw) and wanted to just install standard packages and use standard tools (ie gparted, clonezilla, etc).
I've got btrfs RAID5 running fine.
Had loads of power outages (we had water meeting electrics) and have no problems at all.
Of course, RAID is not a backup, so all my important stuff is on Hetzner too.
I don't really follow the ZFS news, but I understand that resizing / adding new drives is / was a problem, plus, back when I built this, I would've needed kernel patching... there's a higher chance of those causing a problem - for my use case - than btrfs, so if you're like me, just crack on and enjoy the easy life.