I have also ridden thousands of miles in the west and agree CN is excellent. My success rate is more like 99%. I do sometimes find roads on Topo 100k that are not in City Nav and vice versa. So I use both for
trip planning. And I also use Topo 24k sometimes.
Using Mapsource on a PC I see CN minor roads at 1 mile zoom with detail set to highest. On my Montana I see then at .8 mi. And in Basecamp I see them at maybe 3 miles - anyway a lot better than Mapsource.