Good morning jmlebronl,
Thanks for your question. To review, when creating a new project you will add your I/O and Communication modules to the IO configuration inside of the Controller Organizer, as shown in this lesson.
That said, Rockwell does not have a recommended order for their 1756 modules, and they can and will work in any order.
However, if your wireway is divided between 24vdc and 120vac, then you would want to organize your IO modules to support that (i.e. all 24vdc modules on one side, and all 120vac modules on another.)
As far as Controllers and Comm modules, most engineers design systems with the controller in the first slot, followed by the communications modules, but this order is not required.
As far as VFDs, as shown later in the course, where they go depends on how they are connected.
Hope this helps,
Instructor at The Automation School