Aprons aren't required. I haven't been using one but I do get all gunked up. The woodworkers turning apron would work best as it covers your shoulders. When getting splattered it's usually from the waist up. Ya might want to consider a hat of some type or a shower cap.
As for wheel size, it depends on the rpm of the motor. With greaseless compounds 3600 fpm surface speed is almost too fast as it is easy to burn the metal but 1100 fps may be too slow. I feel between 2700 and 3600 if a good range. To calculate surface speed: SFPM = 1/4 x diameter of Wheel x RPM (revs of spindle per min.)