Thanks for the shout-out ECG! I meant rail cars and good wagons when I said trucks, but your idea about having random trains run around and head across the map is great! You could add sidings and shunting yards where they can travel to and rest, that would be great detailing you lines. I can't wait to see what you do with the signal boxes, coaling depot's, and other random decorative details you decide to place in future videos, hope to see you do so much more.

The letters after a wheel arrangement refer to the tank type on a tank engine. T for side tank, ST for saddle tank, WT for well tank and BT for back tank

For the green, try the darkest option between the other darkest greens, might be better. Also the rod that connects the wheels is called a coupling rod, and the rod going from the cylinders to the wheels is called a connecting rod.