I'm kinda on a lazy mood so I'll keep this short. >_> Against Ganon...
- Spam your turnips effectively. He's so big target and his moves are ineffective to knock away turnips it's easy to spam against him. Plus he's slow runner. Turnips followed by aerials own g-man.
- Ganon will outspace peach everytime, but what peach player can do is be faster. Nairs are way too effective when it comes to being fast, not forgetting peach's bair when using evasion & punishment tactics. Be vary of ganon's using retreating fairs to punish you and double jumping to dairs/aerials to punish your turnip approaches. Rising nair can kill his dairing attemps as nicely as it does with Falcon, as well as cut trough his every aerial attempts.
- Ganon is easy to combo, being so big and slow aerial recovery, so use every chance to pressurise him with aerials and dsmashes and whatever. Lots of stuff sends him into comboes. Low float dair or sh/full jump dair into something works really well too.
- Edgeguarding ganon is child's play, but KO'ing a good ganon might prove a lot more difficult. Turnips of course mess his recovery big time. When edgeguarding, if you know your opponent will tech, do not dsmash but dair instead if he goes for the sweetspot. If he goes even a bit above that, fair and bair connect nicely. Peach can also be mean and grab him out of his up B when he doesn't sweetspot from as low as g-dorf can (since he can't really sweetspot). Remember that good players will always try to tech and dsmash will get peach up B'd.
- Good ganondorf players will edgeguard you with bairs and uairs and reverse uairs. Do not try to get him from above, it will not work. He will cut trough whatever you try to do, so aerial dodge past him if you need to. Recovering from high is the best way, when coming from mid you'll need to use toad, parasol or aerial dodge in most cases to get past his edgeguard. When coming from low, hug walls and prepare to tech if you can. Parasol can cut trough his aerials, but go for the sweetspot or stall with toad/peach bomber.
- G-mans usually use wizard foot as a suprise tactic or as a cc'ed attack, since dsmash and dtilt are way too slow compared to peach's dsmash. Forward B doesn't send peach into comboes at KO %, but it's nasty and fast move, though get's owned by dsmash and other stuff. Ftilt is what ganondorf's will spam against peach since it outspaces her greatly and can be aimed up and downwards. Jab/grab is what they'll mostly do from aerials, especially fair, which can be spaced so that peach cannot grab g-dorf.