Rearguard Falls is a beautiful waterfall near Mount Robson Provincial Park. A short trail (600m return) leads downhill from the roadside parking area down to several viewpoints over the wide waterfall on the Fraser River. There are some stairs with handrails.
In September, it is possible to see Chinook (the largest of the Pacific salmon) attempting to pass the falls. Later in the month, some of the trees around the waterfall turn golden.
If you have to choose between Rearguard Falls and Overlander Falls due to time, my vote goes to Rearguard Falls. Both are lovely to see but Rearguard is a little prettier.