I mean sure, but technically everything can be good as a mixup lol

I disagree. It's ok as a mixup to catch your opponent offguard when they think you're just going to grab ledge

Fast fall after the wavedash. Although this is pretty much not useful except for style points since you won't have the invulnerability from grabbing the ledge. 

Pretty new Melee Sheik main here - how do I wavedash off the stage and, instead of grabbing the ledge, just fall backwards into a quick double jump bair edgeguard?  I've tried just wavedashing off backwards, but I always grab the ledge, even if I hold back.  Google found this subreddit for me, so I'm hoping somebody here can help.  Much appreciated! 

Slide off ledge into bair?