I mean, 20TB drives will work in an array just as well as 8TB 😉
Honestly with the price of refurb enterprise drives, it’s really hard not to justify not going that route and just keeping a spare drive formatted on warm standby at all times.
A bit of a digression though, since OP isn’t looking to cram a bunch of drives into an old mini case.
I don’t have specific troubleshooting advice to give, but I have been using an Nvidia Shield Pro as my main streaming device for about 4 years now. It is overpriced for what it is, but it has been rock solid for streaming via both Jellyfin and Plex.
The official Jellyfin app is definitely not as polished as Plex, but it has consistently worked for me on the Shield.