40:60 is too much. Very few characters actually have that strong of an advantage over Doc and Mewtwo is not one of those characters.
I still think it's around 50:50 for both Mario: M2 and Doc: M2. There's a lot of weird intricacies that actually make this matchup not completely one-sided either way.
: The optimal way to play against Doc is to play defensively, because Doc's CQC options are scary and you do not want to be near him. However, unless he does something extremely unsafe, you have to go in and attempt to punish Doc in order to kill him. This is because:
1. Doc has godlike frame data, with respect to both startup and end lag. This means that it's not as easy to bait Doc into doing something unsafe. Most of the time, you have to outmaneuver him in order to punish him, which also involves trying to approach him cautiously.
2. Sheet reflects Shadowball. Not a big game changer and not an automatic win for Doc, but it dissuades Mewtwo from using Shadowball as much. It also means that Mewtwo cannot always snipe Doc from long range and has to go in. Sheet also helps Doc microspace since the lack of a stalling property allows Doc to Wavebounce/B-reverse, similar to how Mewtwo's Confusion works, but without the height gain.
3. Mewtwo does not have any incredibly disjointed aerials that are worth using in neutral. Fair is the closest thing and it is good enough to be respected by Doc, but it is nothing compared to disjointed aerials like Marth/Lucina/Corrin Fair, Ike/Cloud Nair, etc. Bair has range, but it's pretty slow and laggy. Doc can wall out Mewtwo similarly with Bair.
Going in on Doc is risky because any mistake will result in you getting hit by moves like:
Up-B OOS which can kill.
Up-Smash (OOS) which can also kill.
Bair, which can kill, and at worst, inflict 14% damage.
Grab -> Combos (Up Air, Back Air, Fair, Down-B). Also the occasional footstool combo listed above. Down-Throw Fair works but the range isn't that great. Jab 1-Up-B is a cute setup that also works at higher percents.
Down-B, which will just stop any momentum that a Mewtwo might have had.
When it comes to edgeguarding Doc, Mewtwo does not have some special advantage over Doc because of his sub par recovery. Smarter Doc players will conserve their options, know how to mix up their recovery, and be wary of how high they are relative to the platform. Don't just run off Nair/Fair because you expected the Doc to waste their double jump. If you guess right, free stock.
Edgeguarding Mewtwo is a bit harder, but Down-B is such a strong option offstage because the active hitboxes will intercept and usually beat out other moves. The last hit is pretty strong on the sides of the stage. On top of that, Doc can also semi-spike with Down-B, but this is not as reliable.
Mewtwo's KO potential is very good, as is Doc's, but the thing that Mewtwo has over Doc is his superior mobility. This is what Mewtwo needs to take advantage of when fighting against a Doc. Implement a hit and run game, don't throw out projectiles unless you are absolutely sure that Doc will get hit by it or be forced to air dodge and get punished, go in for punishes (and be very careful when going in) and quick bursts of damage.
Overall, while Mewtwo has better mobility, he doesn't really force Doc to approach as much as he wants to. Doc has safe buttons, but he has a similar problem forcing Mewtwo to approach him because of his sub par mobility and mediocre projectile. So both sides have to work hard to get hits safely.
Oh, and just for convenience, I don't mind if Mario and Doc are lumped together, but they are different enough to warrant different strategies.
EDIT: I want to talk about Mario as well, but I will do it later.