MapSource no longer supports the RealTime Track Plotting function.
That refers to plotting your tracks on a map in your PC, not in your GPSR. Garmin split this function off into a separate free program, Nroute. Using the MapSource program, you can load whatever Garmin maps that you purchase into the GPSR, which will show your track just fine.
when I turn off my GPS to save batteries, will it continue to create my track?
No. However, one of the great advantages of a mapping receiver over the simple ones comes when you go off route. Just locate where you want to go on the map, press Go To, and it marks a route on the map. (Maybe not the best route, but a route.) No need for a track to follow back.
The receiver gives you turn-by-turn directions along the route. If you don't like the route it chose, just set off on another likely road. In about a quarter mile, it will ask you if you want it to calculate a new route using this road.