I have some Mewtwo tech to share with you guys.
Are you talking about this?
You get 4-5 frames less landing lag using teleport like that. It seems to work by using it at a certain height, more precisely at the top height of your first jump.
In regards to this, here's one trick you can do: Full Hop -> Immediate Airdodge -> Do what the above image does.
By doing this, not only do you make the move slightly safer to do, but also easier to time since the airdodge ends at around the perfect height to be able to pull this off more consistently.
Of course, it's still a bit difficult to do consistently, but it can be done with practice.
Another thing you can perfectly time using this trick is this: Full Hop -> Immediate Airdodge -> Fully Charged Shadowball.
Doing this will give you the perfect height to slide across the ground with a fully charged Shadowball. And like the teleport technique above, it becomes safer since you are airdodging.
I've also been able to get U-Air -> B-Air (and the true combo set ups) although it's really situational depending on how your U-Air hit the opponent and which direction he was knocked back..
In regards to this, SH Uair (sweetspotted) -> Land -> Followup is a very risky/tricky but rewarding setup that can lead into some unique combos.
Uair -> Grab
Uair -> Jab 1
Uair -> Utilt
Uair -> Usmash
Uair -> Fair
Uair -> Uair
Of course, the reason why these are so risky are due to two factors. One, because these are mostly heavily percent specific. And two, being that the front sweetspoted hitbox of Uair...well, it's almost like you have to hit with his body instead of his tail. :/
However, I have discovered something interesting with SH Uair as a setup tool: The reverse sweetspoted hitbox of the move, for these purposes, is larger than the front hitbox. And thus, by having Mewtwo facing away from your opponent instead of towards them, the chances at which you can land the sweetspot of Uair increases.
By doing this trick, the following thus becomes possible:
Reverse Uair -> Turnaround Grab
Reverse Uair -> Turnaround Jab 1
Reverse Uair -> Utilt
Reverse Uair -> Usmash
Reverse Uair -> Turnaround Fair
Reverse Uair -> Bair
Reverse Uair -> Uair
Do take note that because you have to turn around for some of these attacks to connect, you lose out on a couple of frames. Thankfully, sweetspotted Uair causes a good amount of hitstun at around 50% on Mario. So you can start trying these combos out at around that percent.
The applications of SH sweetspoted Uair are still limited even with this technique though, as they are still heavily percent based. But reversing Uair can help with the range situation a little bit, even if you lose out a bit on frame advantage.
Also, because your back is facing towards the opponent, you can mixup a reverse SH Uair with Bair to further increase your range. Or if you really want to confuse your opponent: Confusion, Fully Charged Shadowball, Teleport, and Air Dodge are all valid escape options depending on the situation.
Lastly, perfectly short-hopped Dair is a decent KO move on the stage that can catch opponents by surprise sometimes. And you won't suffer any landing lag if you perfectly time it. Unfortunately it doesn't kill as early as some of his other options, but it's a nice trick to try out in certain situations.