As you can see by yourself, I'm a huge fan of Snowbird.
Well, let's go straight to the points (no pun intended):
1- Wikipedia: "When she takes the form of an animal whose mass and volume are less than those of a human being, she became a human-sized version of that animal."
This is obvious BS. It's not true. I've always assumed Narya can "shrink" in the same way she can "enlarge" herself in order to replicate a given animal. When she converts into an owl, it's not a human-sized owl, it's an "ordinary" looking owl. Or not? I'm confused a bit.
2- I assume her new body came from some cells of her former body STILL left on Earth. So technically, it was a sort of spontaneous, mystical clonation which generated a new body, identical to the previous one.
This doesn't explain why Wanda managed to come back as Walter, being Snowbird's original body the one he was using. Maybe, shapeshifting capabilities combined with some mystical will? Snowbird's spirit did it.
3- We know Narya's hidden, default appearance is that of a "monster". Only the face or even the body? We just "spotted" her monster face, never the body. Or not?