Gee, I'm getting confused here myself. Just kidding.
You got everything there you need. But let's do a quick review anyway.
First, the route files. Install in this order:
Canton
Suddenly
Thompson
Second, the rollingstock files. Install in this order:
Canton Rollingstock 3a
Canton Rollingstock 3b
Canton Rollingstock 3c
That's all there is to it. However, there is a Thompson patch and another 8 activities you can install after doing the above installs. See the update section of this forum for those.
Now to answer your question:
I think the confusion comes from for some people where they are familiar with these products and think of them as sold separately (some assembly required

). But when they see the name Canton-Suddenly-Thompson they are thinking its a whole different animal. No, they are the same. Whether you purchase the sections separately or in a bundle like you did, they are the same. Even the CD is exactly the same as the downloads. No difference. The only reason for the CD is because many folks are still on dial-up and it would be risky or take too long to download the entire route content.
So what you got is Canton, the Suddenly expansion and the Thompson expansion. The rollingstock is graciously donated by Dick Cowen and his many minions of helpers who have refined and beta the rollingstock so you get a complete and immersive setting for railroading. So you got everything.
Rich Garber