Iunno what to say or what you're actually looking for so I'll just drop whatever comes to mind.
Pivots are crazy good with Marth. Fading back fairs, late fairs and double fairs are all pretty different and good. I also like to Nair enemies in platforms. I like using WD Dtilt to stop people from dash dancing. shieldstop fading back fair sounds like a crazy good option that i never do so you could try that.
Marth has some interesting no impact landings on battlefield, by instantly double jumping to the side platform, running/wavedashing off the side platform and double jumping to the top one and I'm p sure that you can hax dash from the ledge and double jump to land on the side platform with no impact.
If you wavedash back and then dash immediately the momentum makes your dash extremely short, but your dash attack still reaches farther so you can bait some reactions like get up attack with that, you can also boost grab instead of dash attack.