Good question It's work only DC mode
In general, this is a rather complicated system, and I just cannot describe it simple.
Another way of looking at it is if I want to drive a single train what Arduino bits do I need to buy?...RPS ... In my working experience, the "real" experts I dealt with (physics, engineering, economics) had no trouble explaining themselves in simple language for "ordinary folk".
Video and link to sketch for an one train.