Here is a drawing I use in the Alpine courses to explain the split fence and faults.
Outside fence is usually better for cabinet parts if workpieces are short. But do not use an outside fence without a feeder. With no feeder split fence is better.
Changing out wheels to narrow is not necessary unless your outside fence is same height or higher than the workpiece. I use thin fences when doing this just to avoid the hassle of changing wheels.
