I've had to resort to multiple apps and they don't work GREAT even when combined. I was just complaining about this!
I have Auto Photo Cut Paste for cutting faces/other parts out of photos fairly cleanly, and Picsart for actually combining/putting it together, but the Picsart tools seem kind of limited. It's not a full Photoshop replacement.
if it gives you an idea of what's possible. Face removed for anonymity.