In the first vid, your platform dashing is great, but your grounded wavedashes were angled poorly, and were quite short.
In the third vid when you fought sheik, you rarely seized the opportunity to combo. I noticed that after landing a grounded dair, you would just wait to see how the sheik reacted. Instead, you should have L-cancelled, and done another SHFFLed dair, because she bounced to the perfect height and would not have had a chance to interrupt it. Also, you lacked complex mind games, although I may have seen a couple minor ones. Near the end of the match, starting at about 4:52, you two just took turns attacking forward, rolling backwards, and repeating...thus, nobody was making contact. Instead, you should have noted that sheik was going to roll backwards, and counter by attacking in place, or even doing a forward-B towards the wall, that way you would have snagged her, but if you had missed, the wall would cancel the attack. Lastly, you missed almost all of your best opportunities to shield grab her F-smash, which is the easiest attack of her arsenal to catch. Finally, don't play at that stage, the ships interfere.
You've just gotta chaingrab sheik! Gets you an easy 90% advantage, and maybe a kill