Upgrading 10-year-old hardware

[TheDreadPirate]

TLDR; 4 cores is fine for what you're trying to run, since you would have a dedicated GPU. Definitely get 32GB of RAM. If you do use Docker/Podman/Portainer, only do that for your other apps. I wouldn't recommend running Jellyfin in a container on Windows due to limitations in supported GPUs for passthrough to the container (Nvidia only is my understanding).

Check the Jellyfin dashboard to help locate where your files are. It looks like your Jellyfin app data is in your user folder instead of C:\ProgramData\Jellyfin. When Jellyfin is run as admin it will be in ProgramData, if run as an unprivileged user it will be stored in their home directory. The two folders you mentioned have SOME of your data, but there should also be a "Server" folder somewhere. If restarted Jellyfin and then looked in your Jellyfin log, it will print ALL of the directories that have your Jellyfin data.

When migrating to a new host, your Jellyfin app data MUST be located in EXACTLY the same paths as on the original host. A lot of files are referenced by their absolute path.