A problem I have encountered with Google maps is dirt roads are not distinguished from paved. Also Google has routed me on rail to trails that were still just ballast. So Google for me is just a general direction reference. I also rely heavily on Gazatteer atlases when available. I don't have GPS so I carry paper maps. You don't have to plan your route in super detail. When you are out there cycling, local people are more than happy to help you with a route to your immediate destination.