For example, is it possible for voters (or anyone else) to change the democrats superdelegates' votes? In the current race, it seems like Sanders and Clinton are quite close, and the superdelegates will be the deciding factor. It sounds like to me the superdelegates are essentially pledged and will assure Clinton's victory, but I'm not well-read on the subject.
Superdelegates are not bound by any official method. That is, they can announce who they plan to vote for, or promise to vote for a particular candidate, however, until the vote is actually cast, they can change their minds at any time.
Given who they are, their pledges and promises may not be worth the paper that they are (not) written on.