Not exactly sure what you're asking. If it's about "symbols" that you place on the map in Topo!, you can right click and select the "modify style" button and go from there.
If you are talking about actual waypoints which is what your GPS imports, you can only turn them on and off, which is a setting available in the Preferences under Waypoint Label Display. You can select exactly what information displays (name, coordinates, etc.), but not how it appears.
I generally keep mine turned off because if I need to know what it is I can right-click on it, and if I upload it to my GPS it shows up there with the name anyway.
Highway to hell