Last time I checked, Minnesota isn't really known to have many mountains. If there are no mountains in real life, high-resolution terrain mesh will not create them. Flat is flat, no matter what the resolution. Best you're gonna see in Minnesota are subtle undulations.
Ultimate Terrain will have no effect on the terrain mesh other than to make lakes, rivers, streams, and roads more accurate, so turning it off won't have any effect on the terrain mesh.
If you want to compare and see the best results with the high-res terrain, go to a mountainous area and fly around. I'm sure you find some good stuff over a state or two in the Dakotas, the Rockies, and places like that. Minnesota is not the best place to showcase high-resolution terrain mesh