The QM references I use serve only as a demonstration. A lot of people have heard about the double-slit experiment, they perhaps also saw some drawings how it works, but never actually saw/conducted one. So, when it comes to the role of an observer and consciousness in this process, my main question is simply this: if conscious observation is responsible for collapse of wave into particle, how is it possible that we can consciously observe the wave itself (interference pattern)?

The simplest explanation to me is that conscious observation has no play in this. Another possibility could be that, if conscious observation is, indeed, the cause of collapse, each subjective observation collapses the same modified “data set”. The net result in both cases is the same: existence of objective constraints.

When it comes to what can be observed: in this dream, human is created and human mind rules completely only over its own creations. In the world in which it is created, human mind can only focus attention on its responses – technically, you assemble a different perception of the same world. You see here and now through a different lens. Each of those realms can have different rules, but they all describe the same world. (Plus, you can have your day/night-dream overlaid on top of it.)

So, I don't say that you cannot experience walking through walls. I would even go as far as to say that you can even make others experience you walking through walls. I just say, that you are simply traveling without moving (to paraphrase the classic); you fly like sorcerers do, not like birds. You are on Earth, in heaven, hell, and all those other realms simultaneously. And I'm not exactly sure that human can exist after one of its bands gets dissolved. For sure, the echo remains, merges with “intent” (i.e. causality) and thus can even evolve in time, but the human as such is gone as (s)he makes no choices anymore.