Part of the problem/hard work related to subtitles is cleaning up unwanted languages and/or formats.
I don't usually like how PGS subtitles are displayed, and I don't need 20 languages cluttering the list on my way to find what I want.
Tdarr can help here, it can remove unwanted subtitles from the video and I think it can do it without requiring a lot of processing power.
Subtitle sync is another big problem. Bazarr seems to have a section in the settings for this, but not sure how well it works.