oh, boy... these are all very vague questions, but i'll try to answer them.
special tech is basically quick attack canceling and knowing what you can do out of it. know that you can wavedash out of it. something else with quick attack is that you can quick attack downwards and not cancel it. when you do this, there is a very brief amount of time that you're in the air. this is enough time to use a nair, uair, or dair. if you're technical enough you can also l-cancel them.
i've never played a good mewtwo, but the general consensus is around 70-30 pika's favor
edit: MEWTWO's favor...
i can best describe pika's playstyle as annoying. you aren't fox, so don't get carried away with being in your opponent's face, but you can still give off some pressure. quick attack canceling is amazing for mobility, which means that you also don't have to be all over your opponent's face (and you don't want to, as stated earlier). you also have jolts, which are great for making your opponent do stuff. so, he's great at providing pressure and waiting for opponents to mess up.