Garmin maps - selection

[Erik_G]

In my way of learning. I have access to and installed different maps.
To tray out and see if there is any difference.

For Europe. I have Garmin's pre installed maps and OSM.
For South America I bought a map on memory card.
And also downloaded OSM. With and without Topo info.

When I use Base Camp. I can pick the map I want to use.
For searching and calculating.

But for the Garmin Zumo itself. I have not found how I can control what map to use. So I do not know what map the Garmin device is using. When I have two maps covering the same country.

Is there a way that can control and/or know what map to use ?
That I have not found. Or is this something that is not supposed to happen ?
That you install 2 maps that covers a common area.