So after playing with Mewtwo there's a few impressions I have.
1) Far too light to be justified. From an archetype perspective alone, should be at least Rosalina's weight.
2) It is highly unfortunate that Teleport is the way it is. Compared to it's Melee incarnation, it's poor. I was expecting it to at least be better than Meta Knight's Dimensional Cape in terms of safety and ability to dodge. Not only is it poor and unsafe at doing so, it is inconsistent with its sweet spotting. I've had times where I have Teleported to a ledge at 180 degrees, hit the ledge without snapping to it, and popped upwards in free fall.
3) The fact that you cannot combo out of down throw is incredibly stupid, and makes down throw largely useless. It does less damage than forward and back throw, has no kill power, and can't even set up tech situations on stages like Battlefield because the knockback is too low. When will you ever use this?
4) Neutral air out of all of his aerials should be designed with little landing lag in order to utilize its potential. Unfortunately the landing lag it has is too much for it to be used for combo potential or follow ups.
5) Up throw is highly disappointing. It's stronger than most up throws, yes, but why would you ever use it when you can just back throw near a blast zone? I mean, the throw kills at what, 130-140% on most characters? Okay. I can kill people off the top at 80% with Meta Knight. If up throw was to be his defining kill move, it should have been stronger.
6) Mewtwo's neutral is poor largely due to his floatiness. Forward air is excellent, however the time it takes to land when you try to auto cancel it makes you susceptible to dash grabs and dash attacks, or any form of quick movement.
7) I don't have the frame data on Mewtwo's rolls or dodges, but from my experience playing with him they seem atrocious. His techs in particular are really bad, and leave him exposed for far longer than they should.
8) I understand they want to differentiate Lucario and Mewtwo, but was taking away the active hitbox to his charging Shadow Ball really necessary? Arbitrarily nerfing a character.
He's a really cool character, and he has a lot of really great things. Unfortunately, these cool things only seduce you in to using a character with some very real, highly unnecessary flaws. I feel he's solidly low mid tier, maybe high mid tier if someone really good exposed potential with him. Hope this gets patched later when Nintendo realizes no one is using him in like a month.