Example resource pack for GenderBub mod with different models and textures for male and female mobs.
This pack uses Entity Texture Features and Entity Model Features to read the bubgender NBT tag added by GenderBub. When a mob spawns with bubgender: male, ETF applies an alternate texture, and EMF can load a separate model.
You can use this pack as a base to add gender variants for any mob:
.properties file, change the mob ID and point to your textures.jem file and set the condition to the bubgender NBT tag