1st match:
Right off the bat, I'm gonna tell you...learn to DI. First stock of the first match was pretty lame. FURTHERMORE you could have actually survived that edgehog easily if you simply Caped as Snake edgehogged.
Don't pummel or B-throw Snake when he's using grenades. F-throw. It's the fastest throw and your goal in this matchup is to get Snake offstage anyway.
When using fireballs, generally you should focus on using them as approach tools so that you can get in hits on Snake and gain control of the matchup. Letting him grenade camp you back is inadvisable since small mistakes on your part will get punished for much more damage.
When F-smashing Snake, it should almost always be charged. The leanback is capable of baiting Snake, and in the event he DOES block your F-smash when it's charged, it's safer on block and does more shield damage. The other thing that happens is if Snake's first hit F-tilt hits you while you charge any Smash, it bounces you off the ground and his 2nd F-tilt hit I believe does less damage when this happens (I could be wrong). Be careful not to get hit by anything else when charging a Smash though since you take iirc 20% more knockback when hit out of charge stance.
Up-smash uncharged will only reliably kill Snake after like 155ish damage. Charging a properly spaced Sliding Up-smash on the other hand can reliably kill Snake at around 130ish (learn how long you must charge Up-smash to kill him at this range).
You spotdodge a little recklessly, and I think you should replace several of those F-smashes with F-tilts, which aren't hard to land in this matchup and can put Snake in a bad position for easy edgeguards and furthermore are usually much safer on block.
2nd match:
When under a platform, use SH D-air for platform pressure. It's much better than U-air for that purpose.
On Castle Seige 2nd transformation, I usually spam D-tilt on the statues to unstale my other moves. But you didn't really need to break the statues anyway. You should have been using more D-air to pressure Snake from below.
I don't recommend rolling forward too much. It's an okay pocket option, but try not to rely on it (especially if you're about to die) since it's very punishable.
When you shield Snake's F-tilt, depending on spacing (and depending on how stale it is), you can D-smash it out of shield, which is much safer than spotdodging it.
Edgetrapping Snake is easy. Just shield next to the edge and Smash out of shield if he does an attack. N-air can cover edgejump and edgestand very easily. Generally speaking if you do those two things well, Snake will end up needing to edgeroll a lot, which is also punishable with a well-spaced Smash.
All in all though a lot of the match I felt you got hit by F-tilt too much since you had a bad spotdodge habit...