to hover cancel an aerial, you must move mewtwo towards the ground while doing a fair (or any aerial) yes?
Also some things I've notice that are probibally worth mentioning:
1.Im pretty sure, and Im like, pretty sure, that you can extend mewtwo's hover by performing an aerial at the very end of his hover. Down air works best because its so lengthy. Just use it right before mewtwo's eyes stop glowing (wear the armoured mewtwo set, makes eyes easier) and continue hover input on control stick. This is kinda like using a aerial on mewtwo's double jump and getting extra height.
2. In terms of grab kill percentages, I essentially believe that whatever kill barrier is closer is the direction that the throw should be done in( for kills alone, not considering followups). Except for FFallers who will be killed by side throws at percents before up throw will.
3. The most effective edge guarding I do is by running off the ledge and hovering below my opponents and rising up doing a u-air.
4. Similarly, by hovering, using an aerial, and carrying your momentum into the very edge of a platform or the stage, you may perform edge-cancels much easier and reliably than with normal momentum manipulating shenanigans.
5. Downthrow near the edge on a character (ffallers) that can't escape into the air can be regrabbed repeatedly (essentially), until they elect to techroll away towards the edge of the stage or land on the ground. If you read correctly, a disable can be implemented to let you quarter charge a downsmash which is lethal on most characters at the edge of stage.
6. if you only use hover for a very short time, you do not use your double jump. This is pretty nice if mewtwo is hit into the air and is falling while the opponent is looking to juggle. Tap hover right above their highest point they can reach with a jump-uair, and if they do bite, you stay above them and you can fastball an aerial and connect with them. If they don't bite, you only have momentarily slowed your descent, and you've maintained your double jump. also seems pretty useful.