They aren't similar characters at all in my opinion. Neutral b is the only real similarity. I don't know much lucario tech, so my opinion is biased, but mewtwo is great. He requires skilled play though, and you can plan on dying very early.
His combo game is amazing, though a little unconventional. He does not get true combos out of his grabs, but gets great chains from jab, dtilt, uptilt, fair, bair, nair and up air. He has 1 genuine kill throw(up throw), and his back throw also kills from the edge even at lower percents than up throw when at the very edge.
He is great at using mixups. A good mewtwo should not be predictable and needs to be able to react to what choice the opponent makes from his untrue combos.
His smash attacks are very powerful and have good range, thought they are slow. His upsmash is great for catching reads, and there are kill setups leading in to it.
My favorite part of his game is shadowball. You can harass with small shadow balls, or you can charge a full one for damage, and tons of shield pressure. Shield breaks are very possible with this character because of shadowball. You can space a fair on shield, then b reverse a retreating shadowball for a shield break against many characters.
He lacks in a great out of shield option, but is by no means helpless in that position. His nair can carry him to safety out of shield against most characters, and is great at poking through shield also.
Confusion and disable. Both rock in the right situation. Confusion can lead in to combos if the player is caught off guard and tries to land/attack/air dodge out of it. They can jump out of it safely, but it puts them in to an unfavorable position. Confusion is great for stalling in the air, and also for recovering back to stage.
Disable requires a hard read usually, but does has a few setups. Nair-footstool-disable is a high level setup that Aba uses. (I can't ****ing do it. It's crazy difficult) jab-disable is also a very good mixup, but it is not true if they have very fast reaction time, and can be punished if missed.
His air dodge is the best in the game. No debate. It's just the best. Great frame data, you become invisible, and you can act out of it with a nair or fair. Perfection.
His recovery is in my opinion one of the best in the game. Unlike palutena, his teleport makes him invincible. He can't be hit during it. It snaps to ledge easily. You should never be spiked as mewtwo. The combination of his air dodges, side b stalls, wall jump, aerial mobility, the strong aerial game, and his up b's great range, make it very easy to make it back to stage.
Sorry for the lengthy response, I hope it helps!
