Making addons to an existing data pack

Hey, I'm making some data packs that add stuff to an existing pack but that need to be connected to the original pack. Are there good ways to do this or will I just need to work around it each time? Can I replace files in the original pack with edited ones in the addon? I.e. using the "block" filter in mcmeta. Will the game do any sort of prioritization between packs? Cheers