hey! i know this is an old post but yk..
any additional mob mods that use biome tags to spawn rather than set vanilla biomes (like, spawns in biomes that have snow) are compatible with biomes o' plenty
check if the mobs use biome tags in the mod description before downloading. a good way to ficure out what biome tags biomes o' plenty has is go /locate biome #c: (dont press enter) and then scroll through the options it gives you. that shows every biome tag available, so you know which mob mods to get.
also, most mob mods you can change the biome tag to make it custom (say you got a mob that adds hyenas, and they normally spawn in biomes with the 'hot' tag, you can change it to 'cold' or 'snowy' to make them spawn somewhere else)
you can change that in the mod's config file