Spawning entities inside biomes

hello! Same guy again.. im just a bit confused on spawning entities inside biomes. The part i understand right now is that i need to create /worldgen/biome/xbiome.json, however inside that file do i need to specify everything? Im currently looking at a datapack that is like mine, where it creates a new variant of dog and then spawns it in its own biome. However, in this biome json file its got what looks to be the default settings for the biome. Am i able to instead of type out every single setting manually, just add the one im looking for? Hope this made sense.
thank you!!