The Foretrex units are excellent imo. In lieu of a map, consider adding waypoints which are shown on your TOPO map relevant to whatever area you are hiking. Then if need be you can create something of a map using the waypoints. I really like to have different navigation systems set up so they relate to each other.

The Foretrex can work with either UTM or Lat/Long, but I just can’t get my brain to function in UTM so it’s Lat/Long only. Maybe I should learn UTM, but Lat/Long just makes more sense to me.