Nope, they're not overpowered.
For example, Zoe can fire energy blasts from her guantlets that she wears, but that's it, no barries or anything like that. Oh, and don't let her punch you in the face....it will hurt

Zack, his power is manipulating sound, but of course, what he generates, if someone else generates sound, he can't manipulate it. Reason he has a guitar is that that's how he manipulates sound the most, plays on it, then sends it forward as a blast of power sort of thing. And he does use his guitar as a hitting weapon as well. However, he is vulnerable from the back, as in, he can fire in one direction sort of thing.
Drake, he has flight, healing abilities, but not great, just better than humans do, not Wolverine or Hulk kind. He does have some enhanced strength, but again, nothing that strong like Hulk.
And yes, all three can still be killed, which is why they do try to be careful XD