In the long-term, I’m undecided if I want to run a RAID 5 on disks hooked up to my windows system, MacOS or Linux. Considering this, could a DAS, with disks formatted as exfat, be a solid option for me? Any downsides to storing data on exfat or for running raid on exfat?
exFAT solves the cross compatibility issue by removing most features other modern file system have. Fine for some users but not necessarily something I would recommend to someone with a drive array.
On top of that those USB RAID enclosures kinda suck. Unreliable, minimal status info and rebuilds tend to be tricky at best. You should not use them unless you are forced to.
A NAS is likely a much better option and they do not cost that much extra compared to a ~4bay RAID DAS.