@Brett-Bartick I refer you back to this section from above:
The overlay maps are separate to the planning maps and have no effect on route calculations.
Think of them as clear sheets with extra information that you place over the top of the planning map.
The planning map underneath does all of the route calculations.
Each overlay map contains different information. For instance, the OSM overlay shows footpaths and if you zoom in tight there is an incredible level of detail, from post boxes and public toilets to individual trees planted in a city. The Michelin map is famous for its green roads, a road with a green line alongside it indicates a scenic section. Motorway networks are also clearly seen. Google maps are good for showing shops and restaurants. The HERE logistical map is useful for anyone using oversized vehicles as weight and size limits are visible as are environmental zones.
The overlay maps are just additional tools to use while planning your routes.