I'd recommend going with a main and a sub power. That way it makes more sense organically, and you avoid getting people who use like, fire and water or whatever. That also lends the opportunity to have multiple unique powers over the same element (maybe one earth elemental can control plants and another, density.)
Also, if I may, I would suggest that instead of having a shifter who can turn into two different animals entirely, to have them have only one, but be able to use adopted form of their senses or attributes while human. (Ex. Heightened senses of smell or hearing, ability to move quietly or alter their skin colour like a reptile, etc.)