That is a different setting, the "plug brake" issue manifests itself when you have stopped on an incline and take the foot off the brake to press the accelerator pedal.
If the cart starts to roll backwards and the plug brake current setting is too low, the controller will shutdown and you will need to step on the brake to prevent it from rolling backwards.
Increasing the plug brake current will allow the cart to go forward even if it is already rolling backwards.
The "shaking" you are getting on the beginning of the pedal travel may be related to lack of torque depending on your curve.
That curve is really unique to each cart setup as it depends on your max rpm set, the motor, the tire diameter, the terrain conditions and the throttle calibration.
I don't have a copy of my current settings, but the attached image is a good starting point (I used it for a while).
If the cart is still "shaking" at take OFF, increase the torque curve slope (blue line) from the 10% -> 70% shown to 10% -> 80%.