Our maps work with all the firmware and overlay features of Garmin devices, such as Around Me, RoundTrip, Routing, Tracks,  POIs, Waypoints, TrackBack,  Sight n Go, and so on (actual features depend on the Garmin model). 
 

However, if the feature/function is built-in to the pre-installed map on the device, such as Popularity Routes (aka Heatmaps) that many of the modern Edge models, then it is NOT an overlay or firmware function; it can't work with any other maps, as it is embedded in the Garmin pre-installed map only.  
 

Our maps work with overlays and other firmware (system functions) as these are global firmware (system wide) functions/features and not part of a specific map. 
 

In other words, Popularity Routes (Heatmap) function cannot work on any other map, including ALL third party maps (OS/IGN/OSM) because they are embedded in the Garmin pre-installed map only.  The exception to this is if the other map contains Popularity Routes (aka Heatmaps), or you use Garmin Connect to create the route and then send it to your Garmin (as explained by DC Rainmaker below).

If you don't believe me, here's a quote from DC Rainmaker on the subject:

"Last but not least – note that Garmin does add ‘special sauce’ to their maps – most notably what they call ‘Trendline Popularity Routing’, which is basically a variant of heatmaps. The main use for this is when you ask the device itself to create a route on the fly (such as roundtrip routing) that it leverages heatmap data to give you routes that people use more often. However, this is only applicable if you create/re-route on the device itself. You can still take advantage of that concept by simply creating the routes on Garmin Connect or Garmin Connect Mobile first, which will use that same data from the cloud."

 

Our maps are designed to be used without a Map Theme set, as these will change the map colours, data shown, etc. as this is what Map Themes do.