To Alvin…
I watched them again, just to remember whats going on! And actually there is no exact answers to your questions but some ideas to reshape your thoughts :
First of all, They, the animations, all are in very detailed action, detail means more voxel, voxerl means more time and more memory!
Just to give an example, I’ve done 2 months ago a simple smoke pass for my deconstruction animation and the length of it was 49 frame, volume is 250 x 250 x 75.
I’ve used 0,85 spacing for this animation. So as you know there are lots of parameters that can change situtation but for my animation this simulation took 1 hour (maybe 5 min up or down) to finish… So, you got the point 
So shading is everything for an realistic achivement but the main parameter for those videos is firstly detail, more voxels…
C ya!
Especially the corridor one… I reckon the lighting/shadows there has a lot to with the effect there which is something i`m struggling with at the moment. Also, how to achieve the effect of the big round dense plumes of smoke evaporating into all those small wisps…