Exactly what everyone else has said. They are a different species all their own. And trust me I know regular(mallard derived) ducks are friendly and beautiful and amazing as well. I have 6, but it is different. Though mine are friendly and they eat out of my hands they dont like to be picked up...
I think they are pure! They have the right beak, legs, tail, etc.... My female who hatched her eggs "quacked" at me once. It doesnt really sound like a reagular ducks quack, but its still a quack. So I would say yes they are Muscovy hens. Oh and they are BEAUTIFUL by the way, so is your other...