Question, though--Can you comment on what it's like in the edgeguarding department, both being edgeguarded and edgeguarding Meta Knight?
(L)edgeguarding MK:
When MK is offstage (or hell, very high up in the air) he has no reason not to go for the ledge first. Attempting to get back onstage right away only means he's going to get juggled. The edgeguarding situation will never get you killed if you mess up (unless you mess up reallllly badly), the worst that can happen is that you get faired or nadoed. If this happens you can just shrug it off, what's mostly too bad is that you lost your chance to ledgeguard (more on that later).
Before you approach him offstage you have to make the choice whether to do it with bair or with fair. Obviously fair is better if you plan on going far offstage since it lasts shorter (so you aren't straining your own recovery too much). Since bair has more range and more killing power, it should be favored when you plan on being a tad aggressive closer to the ledge (obviously you autoselect bair when coming from the ledge).
So what do I do?
If the MK hasn't got his stuff together and whiffs fairs and dairs you can just punish whatever he does. This is NOT the way he should handle the situation so don't have any expectations with regards to this.
It's more likely that he recovers relatively low, say ledge level, in order to prevent too much aggro coming from you. If he comes back higher than that he's more vulnerable to being chased. By going low he also gives himself the chance to counter your attempts of edgeguarding with his uair, which you can
not challenge. If he goes too low you can edgeguard his normal recovery and he'll have to scrooge really low, which you can only really counter with a very well timed fart. Note that this is entirely realistic yet also really annoying and strict to pull off.
When he recovers appropriately as described above he's still somewhat vulnerable to random bairs or fairs from you. Remember that in this situation
you are the one actively putting pressure on him. Real pressure. If you chase him too far and don't reach him in time, he can very simply nado back to the stage. This is what the edgeguarding situation is all about and it can be fairly frustrating to get nadoed several times when being ballzy. The only real counter to nado is baiting it from the right distance, getting your footing back onstage and punishing it. The good thing is that because he already spent a big part of the nado duration traveling back onstage, he can no longer space it too well outside of your punishing range.
What this means is, if you correctly read the nado recovery and handle the situation well, you have yourself a setup for a fsmash. A KILL
However, there are quite a few variables which can make the whole process of predicting and punishing the nado a bit difficult. MK has to start it at the right distance and height if you want to get anything out of it. It's really hard to describe and you should really just experience with it until you get the estimation skills required down.
If he doesn't recover with nado you can get fairs and bairs, it's simple as that (unless, as said, he scrooges).
Ledgeguarding MK
Even though the two terms are technically the same, I use the term ledgeguarding for withholding your opponent from getting back onstage from the ledge.
MK is safe here, do not make any attempts to get within the range of his uair or fair (through the stage) unless you want to do something ******** like an anti-plank fart (of which I'm not even sure it's possible since you can't fastfall it, I wouldn't bother trying myself unless I'm at a stock deficit and getting timed out).
MK's options are limited, actually not practically existent. They all rely on you messing up and this is really the one point on which every Wario out there (yes, also Glutonny or whoever your idol is) can improve and will always be able to improve. It's all a matter of timing ftilt.
Ftilt. Beats. Everything. This counts for almost every matchup, the move seems to be designed for use when ledgeguarding. Its range is preposterous and the move design is almost to abstract for me to handle. It beats everything because the cooldown lag is nonexistent, if MK does a ledgejump the cooldown lag is so low that you are able to react to it in time. His ledgejump puts him at an awful height, exactly the height on which he can be juggled. If they commit to this just react and exploit the situation accordingly. Ledgeroll takes too long, especially after 100%, same counts for normal getup. The setup is fairly simple: you stand outside of ledge attack range and you wait for him to get up.
What is the best way MK can deal with this
It's simply airdodging back onstage. That, or perfectly space a nado so that the ftilt doesn't hit him and he can circumvent the active hitbox. That's where your timing comes in: time the ftilt so that you either catch his 2 frame landing or that you beat out nado with it. It's annoyingly strict and takes a lot of practice to get down. Note that if you expect the airdodge landing you can also go in with a nair and punish it more easily, yet this is a commitment that loses to MK opting not to act at all.
At any case, you have the advantage even when he does get back up. MK needs space to execute his moves safely, don't stress when he gets back.
A bit too busy to bring this any further, more later...