I read OP’s question as him streaming from a Jellyfin server to this box, not using this box as a Jellyfin server itself. Could be wrong, though.
Also, it’s my understanding that transcoding is 100% about hardware support for the codecs and that integrated graphics that have it (TL;DR: 12th gen Intel) are going to perform pretty much just as well as even a high-end discrete gaming GPU for that task.
(I say “gaming” GPU because I was reading about the Arc Pro B50 the other day and it has two separate sets of transcoding hardware, so it presumably would actually perform better in terms of the number of simultaneous streams it could handle. But short of something like that, it apparently doesn’t make much difference.)
IMO the trouble is that there are so many of the things now that I need a damn flowchart to understand how they work together and which ones I need.
(No, seriously: I want to set up an *arr stack but don’t understand how. Could somebody please send me a flowchart??)