Originally Posted by
atwl77
2) I find that the Garmin works with the course better if the maps match. For example, I have OSM Cycle maps loaded into my Garmin, so when I build the route in RWGPS I also make sure it is using OSM Cycle maps as I build the route. It is fine to switch to other maps for reference purposes (for example, I find the default Google map shows more landmarks and POIs than OSM), just as long as I switch back to OSM Cycle before plotting additional points along the route.
The 520 only displays maps (it doesn't matter what maps are installed as far as how it does navigation). The map installed on the 520 (not the plus) covers a lot of area but it does not have any detail (the 520 doesn't have much memory, which makes installing maps a pain).
The newer Garmins (like the 520+) come with (detailed) maps based on OSM and include the cycle paths (that are included on the OSM cycle maps). So, there's no need to use OSM maps to replace the OSM maps it already has.
If you need maps for regions not covered by the installed maps, use one of the sources of free OSM maps that are available (that is, don't buy maps).