If you reencode to a more efficient codec, you can save ridiculous amounts of space. If you’re interested in reencoding and are willing to play with self hosting, look into Tdarr, it’s an app that can reencode your whole library. Been using it for a while after switching from my personal solution has been wonderful. I just put files into my media directories and it picks it up, reencodes the file and replaces the original if everything checks out.