The jellyfin DB itself is unfortunately sqlite instead of being DB agnostic. Maybe you could hack together something such that only one node handles writes and everyone else handles reads... if getting multiple cheap nodes gets your more bandwidth. I have to imagine that jellyfin fairly quickly stops being in charge of the media stream directly.
But yeah I think the transcoding and the size of your data pipe is the only "hard" part. The DB read/writes themselves are going to not be an issue (I think)
If Jellyfin ever fixes the mountain of bugs from the "upgrade". They aren't even acknowledging major bugs that make Jellyfin unusable for like 20% of users.
Do not upgrade Jellyfin if you have a sizeable library. Backup first if you do.
I only have an cpu with hardware acceleration that is used for transcoding and even that can handle a couple of streams transcoding simultaneously. The biggest thing is getting people to use clients that support direct play.
Yes, it was annoying, SQLite sucks as single source of truth for clusters, and it cost less than $100 to just buy hardware that can handle multiple high res transcoding sessions at once, but not 20 households' worth.
I'm wanting to set it up for around 20 households to share, and with transcoding that exceeds a single (cheap) node.