I read the FAQ on the TSW6 starter pack but unless i missed it.I didn't see any list of included trains to try unless it only the 4 pictured.If i remember from previous versions of the training center there where a few different types of wagons and coaches as well.
The Training Center/Free Starter Pack now includes the SD40-2, BR 146, Class 323, Class 66, and the 8F steam locomotive.
It’s pretty bland the trains you get, I would really expect them to add one for tap changer trains and a more classic diesel like the class 47 which is sometimes more complex for newer players