Hi Bob,
In a word 'no'
Slow jog is by default set at 80% (I think - long while since I made a fresh install) increasing it to 100% will give maximum speed. The 'shift' key overrides the slow jog setting making it 100%.
In Motor Tuning, the Velocity of each axis should, ideally, be set 30% lower than the speed at which the motors nearly but just don't quite stall. Similar with Acceleration.
Within your Gcode the G0 / G00 moves are rapids and the axis will travel at the Velocity set in Motor Tuning - the G01 / G02 / G03 moves are at the Velocity determined by the Feed-rate which has been set (within the Gcode program) by the F#### command.
The Mach3 manual explains all this much better than I can.
http://www.machsupport.com/help-learning/product-manuals/Tweakie.