I have always used small, cheap devices for the servers and NAS storage. I actually had a NAS for a long time to backup my personal devices, too, even before self-hosting. The NAS uses cheaper, slower drives but larger anf more of them and in RAID configuration for redundancy because I've had too many drives die on me over the years. And I then use NFS to cache the data locally on the servers which benefit from faster drives which can then be much smaller because they are more expensive per GB.