Well, I once set it up, and both the installation and usage were very simplistic. You couldn't specify anything during the installation except the drive where to install. And since you can't change app paths either (at least through GUI), I wonder if I can take advantage of a secondary drive. Maybe I'll just try it out again. I'm planning on setting up a home server but wonder if Umbrel is good for that.
I've used them all and Yunohost is the best. Very much not ideal but still the best. Has very easy reverse-proxy management and a huge library.
It doesn't incorporate any sort of RAID management, if that's what you're asking. AFAIK you'll need to use unRAID or TrueNAS for that. Be aware TrueNAS is in the process of breaking the entire third-party repository of TrueCharts by switching to Docker.
Okay, that's more direct. I would assume all packages have static paths that aren't able to be changed through the GUI. I would read their docs and find out about that specific angle to try and sort it out. Also, symlinks are a thing, but you may create race conditions that particular OS may not expect if your mount timing is not absolutely bulletproof and perfect every single boot.