Road restrictions come in all sizes. As far as height limitations, check out this website: Low Clearances
Maintained by AITA, it lists by state all roads with any overhead clearances less than 13' or 13'6", depending on the state.
Weight limits are unlikely to be a common problem, unless you're a very large and heavy coach trying to go down a very small road. In any event, unusual weight limits are almost always posted by signage along the road.
Where the truck or motorhome oriented GPS unit should be very useful is in helping a vehicle of your size avoid dead-ends, sharp turns, or tunnels that would be problematic. We have a Rand McNally we bought last year and have found it to be unreliable in that area.
A simple planning tool that I use (in advance) is to go to Google maps in the sat photo mode and scan the road I want to take. If I see any large trucks, I know the motorhome will be fine.