Garmin nuvi for off road

I’m new to the GPS game. I like the size and the price of the nuvi compared to the hand held models. But i have been told that the nuviwill not work properly in the mountains with Dans North Cumberland trail maps installed. I see people no here with them installed on there :redrzr: an love them. Is there a certain model that I need to look for or does it matter. Any information would be greatly appreciated.