I use Little Nav Map.

It's free, comprehensive, and links to MSFS in beta build (unless that changed recently and now it's in main build). Very handy to have a real-world map on the other monitor, also shows you a terrain profile visualisation too so you can see how close to the hills you're going to get. Also it's pretty good for navigating around an airport.

"They might look the same, but they don't taste the same."