The first fic was one in which Tony’s power involved something like energy manipulation, and I think it was a long fic. Storm (and Logan) also played a pretty big part in the fic; I remember reading that mutants advanced to the next “level” if they won a match - I know there was a very detailed description of Storm and Tony’s match. Tony was making forcefields and energy balls, so I definitely think his power is something like that.
The second fic is one where Tony and the teens were kidnapped (it was fairly far along in the fic) and I think the villains may have been trying to remove their mutations or something? The only teen I know was definitely kidnapped is Kitty; Rogue probably was as well. I don’t think the Avengers knew he was a mutant? I definitely remember that Fury tipped the villains off, but he was also definitely being controlled.