First match!
Hold away when you get waveshined and you won't get grabbed as easily. Shffl your uairs and use them at the last moment if possible to give your opponent less time to recover before you throw out your next attack and also try to hit with the tip. It's good that you can shdf but you shouldn't use it unless you're sure you're going to land the first one, so not on the approach. Shffl your fairs so that you hit with the tip, low towards the ground and you'll have a lot more opportunities to combo.
Your reaction time is a little slow. I know you want to evaluate the situation and see what to do, but often times the wrong thing is better than nothing at all. At least spotdodge or wavedash away or shield or something, so you don't get punished in the meantime.
When Fox is recovering and he's really close to the stage, just hit him while he's charing his Fire Fox. It's fairly easy with your range. Also, if you must wait for him to get to the stage (bad idea, as he can ledgetech) then you should move back so that the tip hits him, or at least the outer parts of your sword so you don't get hit by the Fire Fox.
Jump cancel your grabs. Also, you're spending too much time in the air. Against Fox - especially one who isn't shooting lasers at all - you should ideally be at shorthop height or below, so you don't get hit by uairs and such. If you're that high in the air, it's also fairly easy for Fox to dash behind you and punish from there.
If Fox is standing right at the ledge, your get-up attack below 100% won't hit him, so shffl a nair instead. Work on your recovery a little so that you don't get gimped by shines and bairs and you'll live a lot longer.
Second match!
Oooh, Marth on Ganon. That's a fun one.
Same problem with the high fairs. I dunno, a lot of Marths do that. I'm not sure why. L-canceling alone won't get you out of shieldgrabs, if you hit them too high on the shield, they can grab you in the lag time. You don't seem to be grabbing enough, either. Also, when you walltech or ledgetech or whatever, you probably shouldn't hold up, as Marth's horizontal recovery often makes it so that he can't recover. If you must, though, you can either interrupt your outward movement with an attack then immediately DI back towards the stage or you can airdodge back onto the stage.
Don't approach with the dash attack. It's very laggy and very predictable. You're also not hitting with the tip, so it wouldn't do you much good anyway.
You're trying to outprioritize too much on the recovery with the fair. Yes you have a lot of priority, but they can hit you from below or even trade hits with you and you'll come out on the losing side. It's a bad idea.
But yeah, work on your recovery and shffls and grab more. Don't float around so much and try to always be doing something.