All gryphons have avian forequarters (so forelegs, head, shoulders, withers, and wings) and feline hindquarters (hind legs, tail). There's some variation in that some gryphons may have feathers on their tail or fur moving farther up their back and onto their withers but that's about it.
Also, idk if I mentioned it, but for the species mixes, typically the two animals should have a similar build. For example, a falcon might be mixed with a cheetah, since both are built for speed, or a tiger with an eagle, since they're both strength-based.