Size and track work make a difference in a train's running. Scale cars look best, especially when it comes to passenger consists. Small cars are passable, but do not match the visual appeal of long cars and long trains gliding through gentle curves. Of course, on a large pike with tortuous, tight curves, long Heavyweights might not work so well. The Madison would be a better choice, and Classic - sized freights would work well.
Large pikes demand longer trains, provided there are long straightaways and gentle curves.
A freight train of twelve cars looks good, and twenty looks better. Passenger liners can abide five to twelve cars easily. Tightly-curved pikes with less straightaway can handle longer trains, yet will abide small consists well. Small pikes invariably have tight curves. Longer scale cars are at a disadvantage.