I know of the theory, but not really enough to comment. It's fascinating, and more than a little humbling, when you start to think about it. I need to read up some more on String Theory and the like, then perhaps I can add something useful here! Thanks for bringing this up. May They Rise!

I definitely believe in the potential of the multiverse however, I believe that all such universes would be subject to the laws of physics (in other words, there is no universe in which Superman or the Flash or Deadpool actually exist. Batman without a doubt though). The multiverse is an argument in favor of causality determinism in my opinion (that free will doesn't exist and events happen exactly as they do because of all the events that lead up to it in a butterfly effect/domino effect way). As a very simplistic example, if you flip a coin and it's heads, then in another universe it is tails. That means that the coin had to be tails in Universe B because it was heads in Universe A. In other words, because there is a universe for all possible outcomes, the outcomes in our Universe must be what they are because any other outcome would have to be done in the other universes thus making it impossible for Heads to be flipped in Universe B and vice versa. I don't know if I believe that the multiverse is necessarily infinite or just as large as the number of potential outcomes if even that. Or maybe theres only 1 universe or 3 or 42 universes and I only exist in one of them and so do coins.