Couldn't you just ask your dreamguide what they are really ?

I met mine only once, last week, after 1 month of "searching". The dream was too short, but the first (and last) thing I could ask her was "So who are you ? are you created by my mind, or do you come from elsewhere ?". She answered something like (I'm translating to english here) "Or I come from the edge/contours...". I was a bit perplexed, and awoke at this point.

My opinion, a priori, would be that there is no reason that a particular element of a lucid dream should be of a different nature than other DCs/imagery, so I believe a DG is still a product of the subconcious, only more elaborate.

If they are really from an "astral plane", and assuming they don't lie, they should all answer (roughly) the same thing if we ask them about their nature. If they come from our mind, they("it") should each give a different answer depending of the beliefs/fantasy of the subject.

I'll keep asking her until I get a precise answer (when I meet her again), and I'd like other to do the same so that we can compare