Lots of choices for sure. I haven’t built a PC in years but I’d start with looking at the requirements for the Minecraft & Jellyfin server, maybe shoot a bit higher to future-proof the build, then browse PC part picker builds to find combos that have worked well for others?

Best of luck to you.

Hmm interesting problem. A tiny dot of colourful non-toxic paint is what I would try. I did a quick net search and the results I found all mentioned an electronic tag with invasive insertion procedure. If only a tiny belt would stay on…