once I pipe cupcakes with no-butter buttercream (i'll be using solite, an australian shortening) can i just leave them on the bench for a day or do they need to go in the fridge? thanks!

Butter or not, shortening can still melt. Depending on how hot it is, I would refrigerate them some just in case.

I agree that fig'ing any cake will dry it out quicker.  I would box them,. then put the box into a plastic bag OR cover it w/plastic somehow.