I'm currently working on a Datapack for my 1.14 minecraft server. The actual project are loottables, since a lot of my server's players are requesting that killed mobs can drop their head. We had a plugin before that did exactly this, dropping a custom player_head with a custom texture resembeling the killed mob, but it's causing some problems lately and I wanted as few plugins as possible anyway, so i decided to do that with loottables instead, wich is working fine for the most part for now.
However, I've some problems with Mobs that have mutible forms since I haven't found a way to check the NBT data of the mob. So to make it short is there any way to, for example, let a cat with CatType:1 drop something different than a cat with CatType:2 over a general loottable? would be nice if tuxedo cats for example would only drop tuxedo cat heads, Tabby Cats only tabby cat heads and so on, same goes for red and white foxes and any other similar situation^^