I also recently pondered on different levels of lucidity and why certain abilities are unlocked in some dreams and not in others. And then there are dreams where reality checks fail yet trigger no lucidity. And dreams themselves come with varying degree of immersion and different subsequent recall. I was thinking that it would make sense if there is an underlying reason for these different dream qualities emerging.
I’ve developed a rough sketch of a theory that is inspired by what I read in a paper Qu posted and some thoughts I developed while discussing the experience of waking up from a (lucid) dream.
Essentially, let’s ask the question why lucid dreams are different from normal dreams, what makes them special. It’s still all taking part in your sleeping brain, right?
Well, we’re not using the phrase “to wake up inside the dream“ lightly, I think. Some additional parts of your brain become active as you are attaining lucidity. And they fall back asleep as you’re losing it. Now I’m not a brain scientist 
but there are a lot of different parts in the brain for different tasks, like reasoning, self awareness, areas for different thoughts and feelings, etc.
My theory is that different levels of lucidity and of dream types and qualities in general are depending which area of the brain is active, as simple as that. But I’m not aware of anybody doing serious research about parts of your brain turning on and off all while you’re in one and the same dream. If patterns observed in this way match perceived different dream types, then the theory would be confirmed.
But we won’t get that research done so simply, but we can discuss and evaluate theoretically on the forum 
Do you think this idea can be used to describe all lucid and normal dreaming phenomenon you have encountered or is there a contradiction to your experience?