Not sure if this has been brought up yet, but the typing for this new mewtwo has been unconfirmed as of now.
If I may be so bold, I have a hypothesis about this new design and form.
We have seen Sylveon, another new pokemon that has had an unconfirmed typing. It has been theorized that a new type is going to be installed for balance the dragon typing. A proponent for that new type is a fairy type or a sound type (perhaps both?)

My hypothesis on this matter is that this new mew form is one of those new types. Perhaps a fairy type, as this new form is very child-like and has many features that are included in the normal fairy aesthetics.
Now we know that Mewtwo is also receiving a second form as well. So it is extremely possible that we are getting another new typing that has yet to be revealed. This would make sense, given that a new eevee evolution is usually always debuted in pairs.

But all in all, I doubt this new mewform will be purely psychic like the previous mewtwo.