No, they're not the same. Yes CBR is big. But the only time we have ever used the internal bus was to get to our room from the Custom House after check-in. It is a 10 minute walk from the farthest room out to get to OPR and the Main Pool. We like to stay in Jamaica 45 and it's under 5 minutes to walk to OPR and the Main Pool.
As with all the buses on WDW property, the bus will be clearly marked with where it is going. It will either say Internal or the park it is going to. There are electric signs on the front and sides of every bus.