I had a few metadata issues with Jellyfin until I changed the primary metadata source to be the same as what Radarr/Sonarr use so they all the file names match up and I’ve had no issues since.

I also don’t have a notable issues with subtitles in Jellyfin, but maybe your requirements have more friction. Have you tried the (iirc included by default) Jellyfin plugin to automatically download subtitles for your stuff? Or the *arr program that handles subtitles (I forget its name)?