Yes, you can use them without torrenting. They are basically software to organise your media.

You said you added folders with the starting letters. In these folders, do you still have one subfolder per movie? According to Jellyfin documentation each movie should have their own subfolder. Maybe this improves the detection?

https://jellyfin.org/docs/general/server/media/movies/

It could be that your files names are too short. I assume that you will get better results with more information in the file name.

Are you using Radarr/Sonarr by any chance? They can rename your media collection automatically for Jellyfin to recognize it perfectly. I recommend you follow Trash Guide’s recommended naming.

https://trash-guides.info/Radarr/Radarr-recommended-naming-scheme/#jellyfin-tmdb

Then your file names are something like:

{Movie CleanTitle} {(Release Year)} [tmdbid-{TmdbId}] - {{Edition Tags}} {[MediaInfo 3D]}{[Custom Formats]}{[Quality Full]}{[Mediainfo AudioCodec}{ Mediainfo AudioChannels]}{[MediaInfo VideoDynamicRangeType]}{[Mediainfo VideoCodec]}{-Release Group}