how would your guys react to canon group, like how would Mikey react to seeing that they have a family that has been together since almost birth, would he be jealous? Would Donnie be cautious of the Canon Donnie because he's a little more feeling than him or would he be empathetic? How would Leo react to seeing all the scars and bruises of the Canon from the Kraang, would he feel pitty for that Raph or the same, would he be worried about that Donnie from having been inside the technodrome (maybe getting a cancer like sickness from it) would he be empathetic for that Leo? And what about Raph, he's faced with another version of him who also got infected by Kraang but for much less time
Oooooooooooooooo, hmmm, let's see. . .
wt!Mikey always wanted to know who his brothers were. Being exposed to the multiverse was his chance to not only see them all grown up for the first time - it was his chance to finally meet them.
Seeing classic!Mikey would probably lead to some small jealousies, and wt!Mikey wouldn't like it. He would feel that he shouldn't be jealous, and the fact that he is would frustrate him to no end.
Wt!Mikey is happy that there's a version of him that gets the childhood he always wanted. . . but it makes a part of him sad that he couldn't be the one to have it.
wt!Donnie would probably be a bit cautious, but not just with classic!Donnie. He would be wary of all of them out of habit. Who knows if they can be trusted or not?
And I think too, a part of wt!Donnie longs for the days when he could be feeling. Or rather, he misses the days when he could show his emotions without fearing the repercussions of doing so. He misses being carefree, misses that sense of adventure in his life.
Deep down, he'd be glad classic!Donnie can still be his wonderful eccentric self without care. And he would probably try to warn him about what can happen if he's not careful.
wt!Leo has a problem with getting attached to alternate versions of his brothers. To him, there's no separation. Sure, they're different, but a part of him will always see them as his family.
His heart would ache, seeing the things they've been through. But he would also be so so proud of them for getting through all of that; defeating the Kraang was something he couldn't accomplish.
And when it comes to classic!Leo, I think all wt!Leo would see is just a kid who's doing his best to protect the family he loves. No resentment, as you said, just empathetic.
wt!Raph wouldn't really know what to think with his other self. He's still trying to get used to the whole idea of alternate universes, you know?
Classic!Raph was able to break free of the Kraang's control (with some motivation from his family,) something wt!Raph wasn't able to do. He'd probably feel a little inadequate in comparison, like maybe if he'd just tried hard enough, he would've been able to do the same.