[Itredler (OP)]

I understand that string theory allows for the possibility of multiple universes like toast slices stacked in the multi-verse of the toaster with new universes being created as two collide.
Then there is quantum theory that says every event can have multiple outcomes and all can exist. Where does the energy come from to create all these worlds out of every event and where physically are they?

Also do they have any relationship to the multi-verse mentioned above?

[Atomic-S]

Maybe nowhere. How do we know that any of these things exist?