If an Adventure spell leaves the stack in any way other than resolving (most likely by being countered or by failing to resolve because its targets have all become illegal), that card won't be exiled and the spell's controller won't be able to play that card from exile later
Yet so far, aiming for an ink curve has been my main driver for mulligan decisions
The cream of the crop, though, is the Enchanted Rare variant of Belle, Strange but Special, which features borderless artwork of the Disney heroine in her iconic yellow ballroom dress whizzing across library bookshelves on a ladder, books and papers flying everywhere
Ignore the targeting requirements for modes you don't choose
Chrome Host Seedshark, in particular, could wreak massive havoc with the right setup