I think you are good to be prepared. In Idaho, storms come over the mountain with little warning, and it can be a whiteout. I have used Navionics, ONX, and a Garmin 73SV, so I guess you can pick what works for you, and what you will get the most additional function out of. I will say that phones die, especially in the cold, and if you NEED it to work it might pay to have a backup. I know several people that have handheld GPS units that collect dust, now that phones do everything, so you might search EBAY for a cheap Garmin that can lay down a breadcrumb trail to follow back to the car.