I do believe that we have Astral bodies, and I've also heard experiences of people exploring the cosmos in them. I've also had OBEs and have Astral projected a couple times where I did very much have a body, and retained my human state of consciousness.

From my limited understanding there are layers. I think there are dimensions where there is no separation (closer to source, universal consciousness, God, whatever you want to call it), and dimensions where there are individual souls, and soul journeys.

All I can really speak from is my experience, and it was a complete loss of self in every sense of the word. I've always seen that as akin to the death experience under the notion that we all return to source as part of the same consciousness, where there is no separation. But I really don't know what happens when we die. Very possible that we do keep our Astral bodies, atleast for a while.

But yes I absolutely do believe in the higher self, and that interdimensional version of ourselves fits into the framework somehow. I think they're different dimensions which permit a very different nature of experience - individual- dualistic - totality etc.