Since it started, football has had many changes, many of them introduced by FIFA such as red cards, offsides, goalkeepers not being allowed to handle backpasses, VAR, etc. VAR, for example, is not used in all games; I don't know how exactly it works right now for each country/confederation/cup, but at some point it was used by FIFA for continental games, but not for national games or friendly games.
Which made me wonder: How much independence do continental and national confederations have to set rules different to what FIFA sets? Can they do what they want or are they limited by FIFA? How does this work?