I have two questions:
1) What are the better ways to deal with the charged ball projectiles of Samus, Lucario and Mewtwo?
2) What are good ways to deal with Mewtwo? I really hate dealing with this guy, his range with his tail and his insane up smash.
1. Perfect shield to whatever. Ftilt or something.
You can act instantly out of a perfect shield, but you have to tap shield, release, and input the move - quickly and all in consecutive order.
https://www.youtube.com/watch?v=D_Kq75NvbYg&t=0m25s
I still don't see the top Marth players use this really, but it could help them sooo much. I see Mr E use P.Shield to insta-jump fair sometimes, but I don't think it's as good as a grounded option.
You can even simply walk - p.shield - walk, ZeRo does that a lot.
I think it works if you P.shield - roll also.
But you have to be ready for their response, whatever you choose, but it all hinges on getting the perfect shield.
2. I don't have too much problem with Mew2 personally. He is gimmicky and our aerials outrange most anything he can do. You mainly want to avoid getting Faird.
Walk and P.Shield is good, but you also have to read their dash grab attempts. However, mixing in some dash trotting and movement in general will keep him guessing, but when it really comes down to approaching him, I would rely on walking.
From there, you can hit him with Ftilt, raising Nair, hold shield against his Nair or Dash attack.
It's all about the reads, but I think Mewtwos are pretty predictible because they don't usually have to be "tricky" vs Marths, because they aren't used to respecting us, they are used to walking all over us.
(A La Pug -
https://www.youtube.com/watch?v=az2FZlNAdfw)
Pugwest basically did the opposite of my strategy vs Mewtwo, and that's why he got bodied hard, imo. The MU is in Mewtwo's favor, but Marth can make it about 55 - 45 if he knows the MU, imo.