Yes, ringers don't matter for this show or MS. Sometimes, the audience wants to be entertained so pure vocals on MS won't necessarily make you the winner. I do agree that cotton candy is Julianne Hough. The clues match.
I think the moth is Marla Maples. She's very lean. Monica lost weight but she still has a bigger build. Like you mentioned, Michelle is muscular. Plus, Marla did DWTS so she would be willing to do another reality show.
Being on DWTS was also the reason why I was able to guess Bill Nye. Also, I remembered that he and his wife do salsa dancing for fun. Ice cube did a little of that and it did look like an older person doing salsa for enjoyment. The science clues also helped.
I think the sloth is Neil Patrick Harris. He was Doogie Howser M.D. and he was a guest on Glee. He's also done Broadway. Sloth was also funny but coordinated so that would match him.
Don't know who the zebra is. Maybe, it's Ricky Martin because of the comeback clue. But I thought Ricky was a better Latin dancer. But it's also hard to tell with the zebra outfit.
Overall, I think this group was better than Group A especially after Bill was gone.