These controls are identical across all engines. However, the default value of Volume and its control range is dependent on the engine. Also, some volume controls go down to zero, while others (for technical reasons) go down to -60dB.
Vel Sens controls how much incoming velocity level affects the actual volume. The amount reduces as you rotate clockwise, and is disabled if fully clockwise.
Pan moves the apparent sound position from 100% left to 100% right. If Rand is checked then this becomes the position of the centre of left/right randomness and combined with Width gives you the possibility of a small range to one side or the other instead of randomly across the full stereo stage.
Obviously, the random element can't go more than extreme left or right, but instead of clipping to the limits (which would give a bias to the randomness) the actual range is calculated based on the reduced width.