I won't do timestamps on twitch vods, but I've got some general strategies and some specifics.
A couple of thoughts on a quick watch:
1. You do some really clean and technical stuff, but also get punished going for it unnecessarily. For example, on the YS game you try to go for a shine waveland at one point (into presumably waveland off bair, you were doing those a lot), but biff it on the shine, airdodge down, and you get punished. If you're going to go for technical things, you either need to take the zain approach and don't try it in game until you can do it 100 times out of 100 in the lab, or keep it simpler. If you're trying to trick them with shine waveland off bair, why not just fullhop waveland off bair instead? The shine's unnecessary to what you're trying to accomplish, so you're adding frame-tight inputs for no real reason or purpose. Cut out the fat and keep the purpose.
2. You do a nice job with your move choices based on the zone he's in, but you're not paying close attention to *what* he's actually doing in those zones. For example, if he's on the side plat and you're on the ground at the ledge, you're good about doing running sh upairs to snipe him on the platform (instead of the nooby thing of doing advancing sh dair which covers nothing), however, you also have a bad habit of going into 1P mode and not paying attention to how he's getting out of your stuff. There was a point in the DL game where you were on the right side plat and he was dash dancing on the ground under the left side platform. You didn't zone him here at all, you didn't bait him at all, you just ran at him with a SH dair and got punished. It was super obvious: you saw where he was and tried to hit him there, but you weren't paying attention to what he was actually doing (dash dancing to bait out exactly what you did) and got punished. Recognize when he is and isn't committing to something, and don't fall for day 1 baits like that. If you aren't ready to play the micro baiting game, play the macro strategy game. The difference in this specific situation would be that the macro situation would be to fall through the platform with a laser; if it hits you get frame advantage, if he jumps over it, you have stage control, and either way you stay safe. The micro bait would be recognizing that he's trying to bait you, so you go for the counter; either sh towards him with a low laser into dash back, or sh towards him into waveland back to bait out his whiff punish. You did neither, you just went in where you saw him without thinking about what he was doing there.
3. Waiting to see what he does is also going to improve your techchasing game, which at the moment needs work. Generally speaking, when you're techchasing you want to do your best to cover as many options at once as you can, and then react to cover the others. There were many times when you'd get a knockdown, and you'd try to follow up immediately as though you expected them to miss the tech, but then you'd miss the techchase because you were only covering that one option well and failing to follow up on the others. So like, if you get a knockdown with your waveland off bair, then you're going to be knocking them away from you; their best option is to roll away, because you can't really follow up. So in that situation, you'd laser to cover the roll away. But until they actually choose that option, you have several others to cover. If you land off that bair and try to follow up with a dashing sh laser to cover the roll away, you cover that option super hard, but sacrifice your ability to adequately cover the tech in place and tech roll in options. Depending on %, you may also sacrifice your ability to cover the missed tech because your dash will carry you too far. But instead, if you do a *slightly* advancing sh laser towards, you could even position yourself in such a way that you can cover tech roll away *and* missed tech with the laser, tech in place by waiting for it and shining/turnaround uptilting, and tech roll in by having center stage and reacting with an approach. True, you lose the ability to follow up on the most likely option as hard as possible, but you make up for it by not losing so hard to mixups. Your goal is to maintain as good a state of advantage as possible, and there's a bigger risk of losing that advantage when you start going for harder commitments in techchase scenarios. Start with option coverage & reactions, and make reads only when you see a definitive pattern.
4. Last thing I want to point out is that although your move selection in neutral is pretty good, your combo game needs to be much better. I don't think I saw you hit your bread & butter 0-45% dair shine dair shine more than once the whole set; not because he was particularly apt at getting out of it, but because you elected to go for move mixups where none were needed. There was once on the PS game where you did dair shine dair dtilt at like 25%. He got out and you reset to neutral. There was another time on that same game (near the end), where you did dair shine dair shine into shine bair at like 45%; it missed, but even if it hit, it wouldn't have sent him offstage and there would have been no way for you to follow up even had it hit. Now, the thing is that these options have their place, but *only* as DI mixups, and you need to force those mixups out of them. So you need to demonstrate that if he's going to hard DI away your dair shine b&bs every time, that you can follow up with dair shine dair shine dair -> followup into a full combo, every time. You need to show him that you'll cover that option every time, to force him to try to mix up his DI with hard in or SDI behind; *that's* where you're going to get the meaty dtilt mixup (although even there you should still be going for a bnb). If you get a shine on Fox between 0-10%, there is no excuse for not getting them to 45-50% every time, and that's where you have the first mixup to extend the combo. Getting that combo extender is the difference between having to put 3-5 combos together every stock, and being able to consistently kill him off a hit. You should never end a combo early against fox unless it'll send them offstage to the point where they have to burn a dj getting back. So for example, dair shine dair shine nair Fsmash is an early edgeguard against fox; contrast that with dair shine dair shine dair grab -> throw mixup or dair -> dtilt or dair -> turnaround uptilt, which would extend the combo a little longer. Definitely work on getting more off your hits, fox should be scared of your ability to kill them and this guy simply isn't.
Hope that helps, dude. You were doing a lot of stuff well and in particular I liked your move selection in neutral; you played it generally pretty safe and you were spacing well. It's just that as soon as you had the advantage, you didn't have much of a sense of how to keep it.