Map Installation on Garmin Touring Plus

The US version of the Garmin Touring Plus comes with a pre-installed microSD card that contains the following files: gmapprom.img, gmapgc.img, gmapdem.img. I have loaded the Openfietsmap Lite map for France onto a new card and that seems to have worked. However, I’m left wondering if there is some feature or information that I will be missing by not having one or more of the files that were on the pre-installed card. Can I or should I copy the gmapprom.img, gmapgc.img, gmapdem.img files onto my new card?

No, you can and actually have to use the OFM Lite map on its own. I’m using the OpenFietsMap Benelux in the same way to my great satisfaction.

The standard maps on the Edge Touring include some elevation data. This is used for showing route profiles, and creating routes to avoid hills.
Openfietsmap Lite doesn’t contain any elevation data, so these features won’t work.

I presume the gmapdem.img file is the digital elevation model. I don’t know if this will work along with Openfietsmap.

Yes, the DEM map will work with Openfietsmap as well as other maps.