I run scale equipment and 2 rail. I maintain 4 inches overall. I do this in the yards to allow fingers to get in rerail cars if needed. I have found any less, and some larger cars, is just too tight for me to work.
I do not have any articulateds, but I do have 80 ft passener cars. My minimum radius is 52 inches (104 diamter) and I have not issues with things hitting on curves. My largest loco is a 2-10-4.
So I have gone slightly larger than NMRA recommendations on straights, and slightly less on curves for the radius I use.