Some folks did have trouble with the installer from RWTools, and I still don't understand why it exists when the RW package manager already does a good job. So, go for the RW one and make two packs: one asset pack and one with the route only, that helps for updates on the route and saves bandwidth for the download.
You should not pack Rich's assets and not the 3DTrain stuff as those are payware with restricted licenses. Mention them in your readme file instead. For the various freeware items see the included readmes there or contact the authors if you are allowed to pack them up. Most items are already clearly stated as "do whatever you want with it, as long as you don't sell it", but some have reserved the publication rights for themselves.
To find out what assets you used in your route check it with RWTools and print out a complete list. From the developer names in the filepath \Assets\
Dev\stuff you can most of the time find back the single downloads. Ask for the ones you cannot locate, someone will know what and where it is.