Mewtwo´s neutral has a basically a zoning or bait and punish play style forcing opponents to either commit to a defensive option or force them to approach. Being the glass cannon he is , Mewtwo thrives off of safe pressure with his projectiles, aerials and long reaching tilts.
Mewtwo will generally rely on shadow ball to add shield pressure or to stuff approaches. Using uncharged shadow ball is more likely to force an opponent to jump while a half or fully charged shadow ball can force opponents to shield. It is important to mix these up a little but this depends on what you want to follow up with. Do you want to get a grab when your opponent when they shield, or do you want to connect an aerial when they jump. These are just a few examples of what you could potentially do to put your opponent in a bad position. You could use down tilt when an opponent is shielding or you could use neutral air to cross up shield and grab. There are many options to chose from so it´s important to experiment to see what works better in certain situations.
Mewtwo´s forward air is usually safe on shield when buffered from a short hop. This can allow you to space backwards if you don´t want to commit to anything or you can mix this up by buffering another forward air form a double jump. The main downside of using the second fair is that you now need to find a way to land which can be difficult for Mewtwo.This is much safer when you use attack canceling for the move(https://www.youtube.com/watch?v=v1kjQtMaPkE). If you want to be more aggressive you can hit opponents shield while landing with a fair. This is even better when auto canceled since you can act out f the move faster. If your opponent remain in shield then you could follow up with down tilt to add more pressure or you can throw out a fully charged shadow ball. If they let go of shield you will be able to follow up with Fair , Dtilt , and Dash attack to either get them of stage or start a combo.
Down tilt is Mewtwo´s main combo starter as it can lead into most of Mewtwo´s aerials. It is going to be your main tool for spacing while grounded. It is important not to over commit because of Mewtwo having a hurtbox on a large portion of his tail. This can allow you to get clipped at farther distances than normal. That being said it is important to space the move. It is safe on shield at max range and can be used to add shield pressure. You should not spam this because it is unsafe , unless you are trying to read a ledge get up. If that is the case then you can follow up with shadow ball or fair.
When you have the option to approach your opponent or you are forced to there somethings you need to keep in mind. Dashing away form your opponent is an extremely important defensive tool. It allows you to bait attacks so you can wiff punish. This is very safe unless you are near the ledge. This used to control space , but be cautious of your tail and dash attacks. Dashing forward is your primary way to approach and a great way to close distances between you and your opponent. This is a great way to add down tilt and shadow ball pressure. Be mindful of fast attacks and OOS options though. Walking is used for the same purpose but to close off smaller distances. These movements will be primarily used for three things. Connecting a shadow ball, a down tilt, or a grab. You can approach with aerials such a spaced forward air but now you will have to find a way to land.
B-reversing is essentially a momentum switch either on the ground or the air. It is performed by pressing the neutral special button while having forward momentum and in the first few frames of the the move press the opposite direction you are facing. If done correctly you will reverse your movement and be facing the opposite direction.
or + > +
This can be used to fake out movement options which is useful to mix up approaches. A more complicated version of a this tech is a wave bounce which is done by performing a b-reverse and reversing that in a similar manner. However the timing is very strict and can be very inconstant. The easier way of doing this is done by doing a turn around jump and then b-reverse it when using a special. If you want to check out more information on the tech check out the video from my smash corner for more info about this and using macro inputs to perform it (https://www.youtube.com/watch?v=3gbZJn8CHMk).
Teleport canceling or edge canceling is a very useful tech which is done by sliding off a stage or platform and in return you will cancel the free fall animation you would normally be put. (Some specials like Diddy Kong´s side special don´t have a free fall animation). You can use this to play mind games or to mix up landings You can even use this to throw out aerials to approach. The angles of doing this are a lot more difficult to get since the time frame is much more strict than smash 4 for this tech. Generally you will be pointing the control stick at a down and diagonal position wen grounded or when close to platforms. When directly above you should teleport to the left and down.
Note: Do not attempt this in an actual match unless you are confident you can perform this constantly or you will get hard punished or SD.
I will go over more techs and info about Mewtwo latter but I hope you enjoy this guide. Feel free to leave your feedback