On that last point, in my own experience, the size of a space matters much less than how you use it.
I filmed two videos in my tiny appartment almost entirely on top of my coffee table and I was still able to create shots with depth. It's all about using space efficiently.
HO, trackmaster, departing now, wooden railway, and beyond CAN all both look and be written/edited as good or better than a project that flaunts its gauge one. It just takes a lot. Not the same amount of space or money, sure, but still. A lot. And we really take it for granted