Sure, I'll try my best.
Yoshi's Nair acts like a C-C-C-Combo breaker, but I suppose you need not to worry about it if you space your aerials right... probably easier said than done, remember Yoshi is quite the aerobic creature.
Bair is quite disjointed and lasts for a while... can be ACed IIRC.
Then we have Uair... it kills...
Mostly on the money. About the neutral air, though, you are indeed right that it can be outspaced, but you want to be careful about the startup because the hitbox explodes during the first few active frames of the move before it shrinks to what the human eye can see normally.
Okay, specials!
Egg Toss... it will probably force you to approach Yoshi, but it's not so bad since Sonic can just put up his shield from running... in fact you're so fast you shouldn't really have to worry about this too much, just know that Yoshi can throw his Eggs wherever he feels like, so don't end up running right into them whe you tried to avoid them... -_-
How often would you get caught in Yoshi's Neutral-B and transformed into an egg... really...? All I know is that if Yoshi can read you out of breaking out of the shell, you can die... or you can get damage racked up on you depending on how long you are encased in the egg.
Yoshi Bomb is defenitely something to look out for... it works like the Bowser bomb that if done from the ground you will be put right into the path of the next part which is considerably strong. It has some after lag, but usually his sides will be defended, so you will have to punish him from the air. Don't get predictable in your approaches.
Egg roll... hrm... it's lulzy, but I think it works like Sonic's SDR where it will either get beat out with enough priority, or it will knock you out of some stuff, or clank. If you try to beat it with SDR, the result is luckily you will get hit out of it since he will have his fresh (if he even bothers to use it).
Egg Toss most definitely makes Sonic approach as the move can cover up to 85% of Final Destination's ground space and short hop space from any one corner. I don't recommend the run-up-and-shield solution to eggs, since it puts Sonic in a bad position. Out of his shield at the spacing I'm considering (maybe...a little farther than forward tilt range--any closer to that and Yoshi should get punished for letting you so close), Sonic has very few options that can't be outguessed, so I would recommend short hop airdodges and just trying to weave your way through them in general. Running up and shielding is not good for him here.
Don't worry about getting hit while you're encased in the neutral B egg. Just try not to be predictable about when you break free and how you break free.
And don't try to beat Egg Roll. The only moves I've seen Sonic do that beat it are down air and back air. If you do try to beat this move aerially, which is an okay option, I suppose, make sure you pre-emptively space yourself because the move does accelerate itself.
Then we have standard attacks.
His UTilt works like Sonic's... I think... just how vertically disjointed is it?
FTilt can go a little ways, it'll probably push you away if he times it right, or clanks if you were SDRing at him... Not too much window of opportunity for him to mistime it and suffer dead-frames AFAIK. Jab does the same thing as his FTilt, but it being so fast it will clank and then just hit you out.
Fighting Yoshi is like fighting R.O.B., just get close enough where you can't be punished, but if he does anything you will have enough time to punish if you're on your toes. Yoshi's shield is not exactly the best, sure you can't shieldpoke it, but IIRC he cannot react OoS like say Marth can or something. I wonder if he has a different timing for PSing too, if they want to be that crucial in shaving off shield lag...
You won't be gimping Yoshi BTW, he can just airdodge through most if not all of his 2nd jump, so just read his recovery path and wait for him to punish there.
Go for "flat" stages, so that you can find ways around Yoshi and attack.
That's all I can come up with... for now.
Yoshi's up tilt is more vertically disjoint than Sonic's, but it doesn't have the luxury of the very wide horizontally disjoint boxes.
Forward tilt is Yoshi's number 2 ground punisher on Sonic because of it's ridiculous range and speed. It beats or ties with everything short of Sonic's forward smash, which seems to be his only reliable priority hog on the ground (at least when I play him). Even so, I suppose it "technically" beats forward smash on the premise that it's almost twice as fast, so if they are input at the same time, then the tilt would win. Yoshi's number on punisher on the ground is jab and the move is unbelievably amazing.
I have to disagree about comparing Yoshi to R.O.B. Against R.O.B. you can force him into really bad situations by taking advantage of the fact that no matter his playstyle, when you're in R.O.B.'s face up close and harassing him, there is very little he can do that's not ridiculously punishable or predictable. Fighting Yoshi requires a much gayer playstyle, more hit-and-run, lots of low-risk, low-reward gay. Your goal is generally to be as annoying as possible while putting yourself at the least amount of risk. You cannot go in with the mindset of trading hits because it just won't work and in-your-face harassment will be retaliated with Yoshi's intelligent short hop and ground-based punishers.
The one thing I absolutely agree with you on is enlighting your fellow mains that, no, you cannot gimp Yoshi. LOL! You get +10 just for that, sir.
