Mewtwo can F-Air, B-Air, U-Air, and N-Air out of his SHAD. He can also charge/release Shadow Ball before hitting the ground, punish with Disable, Teleport (especially good with ledge cancels), and use Confusion.
All his aerials allow combos (mainly into grab), SHAD U-Air is a good combo starter, SHAD F-Air is fast, combos into grab, SHAD B-Air has really good range and SHAD N-Air is... kinda useless, unless N-Air > Grab is a real thing.
If he uses Shadow Ball or Confusion, he can use B-Reverse/Wavebounce/stuff to shift momentum around. This is especially good with Confusion because SHAD > Confusion allows him to move around and puts him further in the air to bait stuff, so he can punish harder.
Teleport is mainly for escaping potential screw-ups and general movement out of SHAD, and can be really good with ledge cancels because no lag.
Disable is for those hard punishes, but is really scary because if you **** up he's gonna use it and kill you super early.
o also Mewtwo has p good airspeed and he's invisible during his airdodge so yay