Hardware advice

[TheDreadPirate]

You can't really put a specific time on certain hardware. Depending on the settings the same hardware could take a few minutes to transcode a movie or several hours.

You don't need a lot if you choose the right hardware. A mini PC with an Intel N100 with 8GB of RAM could run circles around the setup you're describing because the iGPU in modern Intel CPUs have fantastic media engines. Intel Arc GPUs even more so.

To give better advise I'd need to know your budget, whether you want your Jellyfin server to be separate from your gaming PC, how much hardware you have to recycle, etc.

If it doesn't need to be a gaming PC, and you only have a few users, you really don't need a lot if you choose wisely.