Anime fansubs are sometimes really high quality but sometimes have minor mistakes. Official subs are always ok, and official subs never have opening and ending songs and tend not to translate things like papers and have worse fonts and avoid translators notes as much as they can even if it means localizing. So in conclusion, stan high quality fansubs. Also a lot of times fansubs with song subtitles have romaji at the top that’s highlighted as its being sang and have cool effects sometimes.