Match 1: Let me first say that your spacing is pretty good! You should feel proud that you have a good understanding of what its all about. Ok now for the things I noticed. You missed a handful of cancels, particularly the aerials you do after running off a platform. Be sure to practice those more. At 00:42 you double jumped above the stage at high percents. This is risky. Instead of double jumping simply fall towards the edge and grab it...or air dodge. Any of those two options are safer then double jumping. At 1:00 you got Sheik off the stage and you attempted to hit her with a fair. In those situations use Marth's jab to steal your foe's second jump. Its fast and reliable.
You really need to smooth out your movement. Your Marth's movement isn't smooth just yet, well at least in this vid anyway. Remember to keep your wavedashes as long as possible and reduce the amount of mistakes when wavedashing. Also, learn how to immediately dash away after a SHFFL fair/nair and dash back in and grab. Very pro tech with Marth. Some of your wavelands was sexy, though. You waveland way more then me. lol Your dancing blade idea wasn't a bad idea. Me personally, I'd I hit Sheik with the first forward B and quickly up tilt after. Ledge hop uairs when your opponent is in front of you isn't a wise idea. It lacks frontal range. Stick with ledge hop nairs.
You also need to work on your edge guarding. You made silly mistakes. Bair isn't Marth's only option. Try to run out and fair Sheik during her second jump. Again, Marth's jab is pretty good edge guarding tool as well. Um...and learning to do ledge hop dairs couldn't hurt either.
Match 2: Again, work on canceling those aerials after running off a platform. At 7:21 you got knocked of the stage and you double jumped to grabbed the edge. Remember just continue to fall and grab the ledge. Good job removing Sheik's third stock. Your movement is looking much smoother in this vid, by the way.
Overall, not bad at all. Keep up the good work. XD
