From the South Rim, the Horseshoe Mesa and your own South Kaibab suggestions are very scenic. If you can handle a very long day, "Plateau Point", about 1.5 miles from Indian Gardens on the Bright Angel trail, offers a spectacular "overhang" off the Tonto Platform formation; above the confluence of the Bright Angel Creek and the Colorado River. The Bright Angel itself can be a pack mule highway, but even that has it's own charms...
There are signs suggesting dayhike turnaround times down the corridor. One caution if going up the Bright Angel trail is avoiding climbing "the Devil's corkscrew" in the heat of the day. Pretty scenic looking down on it from the top but even that's a long day.