A little late for the party but I'll answer anyways.
How do you beat...?
-Fox's Top Platform camping?
Well if he's attempting to clock you out, good luck if he's determined. It's hard to force him down if he doesn't have to. If he's just staying there spamming lasers or shielding I usually try to coax him down with missiles, carefully spaced Uairs, etc. Or you could just do absolutely nothing until he realizes camping isn't making the match go anywhere.
It's a bit tricky if he's spacing well and FFing, but WD back or under him and catching him with a spaced tilt usually works. If he's doing it continuously just UpB OoS and shut his face down.
-Shine on shield wd away (the kind that you can't upB)?
WDing straight down allows you do do things faster than releasing the shield button does. Sometimes you can hit him with a grab. WD forward jab works when you want a good hit and run move.
-Fox ledgehogging while you're recovering (usually turns into FF shine DJ bair)?
(I've tried upB, spacing the up B out (bair is 2 big), over shooting the upB (bair is 2 high priority), wall hugging the up b (get shined), grappling the edge (they drop down and shine), grappling the stage (shined again)))
Well a good fox won't let you on the stage ever. All he really has to do is hold the edge and time his shine. If the Fox is unpatient, you can usually coax him into doing something prematurely and get back on. Stalling your grapple timing and spacing with bomb jumps usually does the trick. Sometimes I Uair and poke him, but you need to position yourself well to do that.
-Shiek's running shield (well just running shield in general)?
This is really one of my biggest problems. If you can only answer 1 question answer this one.
Grab lol
Or WD back. Just don't attack the shield, ever, unless you know she can't do anything, which is also never.
-Shiek who is in their dash attack/running shield/running grab range and is moving around on the ground. (WDing, DDing whatever.)
Use move that disrupt her spacing. Tilts (namely Ftilt in my experienced) that are spaced well and Jabs work. As long as you pay attention to where she's going you won't be overwhelmed.
-When shiek shields your Ftilt then WD in-> Shield, wtf do you do?
Dash back, WD back, grab, and pivot ftilt/jab. I use platform WDing for quick getaways.
-What do you do when Shiek fair->shields you? (you're getting hit by the Fair btw.)
Mostly same as above.
-Ganon's standing/retreating Bairs or Fairs
Not much you can do. If they're doing it repeatedly, just time and space moves, then time and space moves more. Jabbing will get you jabbed, ftilted and/or wizard kicked.
-Also how do you escape Ganon's low% combos?
(Cause like if he hits me with pretty much anything it's like 40-60% damage + edgeguard.)
Depends on the combo. He can CG you I think, and combos with Fair can be DI'd, and combos with Dair can be teched.
-Captain Falcon crossing you up.
(Also this means he's already in your space, ie he's broken the WDback barrier and is in Standing SHNair range or is jumping around your shield.)
This just means you should have spaced better. If he's broken the WD back barrier you can WD forward. UB OoS works too.
-Captain Falcon's Full Jump.
(usually from standing (out of shield) and he is positioning for a Dair, Knee, or DJ waveland->shenanigans. (See SS style (that kind of FJing) )
UpB OoS, utilt, Uair, etc. Falcon's easy to predict when he Full jumps or DJs.
-How do you approach a laser camping low %age Falco?
(If try to get into the Ftilt/jab zone they do a pivot laser, a FJ->platform camp, or put safe pressure on that zone.
If I try aerial approach's (Missile->Nair/Fair. Platform Waveland Bair (Spaceballs style)) I get CC->shined.
If I try DashAttacking I get CC->Shined.)
PS their lasers if you want to be cool. Generally better spacing should rid you of this problem though.
How the **** do you edgeguard marth?
Best way, force him to land on the stage with the super duper marth edgeguarder. Back facing the ledge, light shield, and tilt backwards. If he tries to sweetspot, his sword hits you and you tumble back, grabing the ledge. If he Doesn't sweetspot, he'll take the stage, where you can ledgehop aerial him back off.
Yeah bombs can work. Dropping down and nairing works well too.