1. You can shapeshift into anyone and alter your physical appearance as you see fit. You can also take on the physical and mental traits of whomever you shapeshift into and access their skills. You could change your brain to match a genius while retaining your personality, change your muscles to match an athlete, voice to match a singer, etc. You could even mix and match. But, you can only shapeshift into people that are known to have existed and can't push your limits beyond what a human is capable of.
2. You can shapeshift into any animal and copy their traits and abilites. You could simply shapeshift your hand to have razor sharp talons, increase your muscles equal to a gorilla, or shift into full animal form. You could mix and match to have the ultimate combination. You retain your human intelligence. But, you can only shift into animals that have been known to exist, and cannot push past the limits of what that animal is capable of and insects don't count