when you said that Nextcloud might not meet your needs, was your concern specifically the server-side data format?
I'd prefer them as plain files. Technically it doesn’t matter much to me if it's a database, if I have to spin up an S3-compatible API, or if I need to slice up a zvol for it, but I just prefer the files because then I can do zfs snapshots (in which I trust) and backup with restic (in which I trust)
I run 3900X with a 40Gbit fiber, packed with HDDs and nvmes. The box fluctuates around 90-110W use.