>Looking at dreams and out-of-body experiences is interesting to help answer your question.
Two points on this:
OOBE are a different class of experiences. It's a completely different state characterized by theta wave activity whereas mystical experiences are associated with delta and gamma waves. Having a malleable sense of self and experiencing dream-like states aren't equivalent phenomena.
People experience what is traditionally considered real(physical reality) and have naive interpretations of what that is(flat world, anthropomorphize animals, finite universe, etc...). Same goes for any other state of consciousness. An interesting counter example is shared hallucinations in such dream states. If you and someone else experience the same phenomena within the same state it goes from a 1st person experience to a 3rd person experience. That doesn't mean the hallucination is there in a physical sense but at the same time the experience suggests and underlying "realness" to it.
>Dreams can seem just as real as real life so I'd speculate that there is nothing that happens in our brains that can't be explained by our brains chemistry.
That's my point. Finding neural correlates doesn't prove/disprove anything as both sides of the argument often like to believe. The experience of the world is also just brain chemistry. We only know the world through experience(and by association biochemistry) so it's not a useful distinction.