Realistic? None of them. They're all speculative. Non-falsifiable hypotheticals isn't what science is about. As for the ones I like, I like the quantum multiverse, and M-theory. I like them not because I think they're accurate descriptions of nature, but because they invite you to look at the world, "our universe" per say, in a different manner philosophically.

Well, interesting. But overall do you think a Multiverse might actually exist? Or is that something where you say “No, this is rather something that only appears in Sci-Fi Movies etc.“

I think it's something that is impossible to prove as true, and impossible to prove as false. It gains heat because the general public wants there to be a multiverse. I'd rather think about something we can prove.