I want to be able to navigate a course, or just passively show the course while the background is the 100k topo. Is this possible? Or do I have to turn off the course and enter the standard map in order to see the topo lines? Thanks!
You can show both standard map and topo 'map' at the same time and still navigating a course. Activate only those two maps in map settings for your preferred activity app. Run settings-Maps-Configure maps
Just show a course w/o navigating I don't think is possible
You cant have passively display course on map unfortunetly. Epix has that feature and Fenix 5x does not :( I used it on Epix very often (displayin 2-3 tracks in diffirent colors - alternative routes)