well full level makes the sound go at max velocity all the time no matter how hard you push the pad... however with it not turned on, you can tap it lightly for a low level or bang it for full level.
one thing I like messing with is... turn your timing to 1/32 with the full level off. push play and hold the tap tempo button and hold any pad down (for example the closed high hat) and hold the pad harder and softer.
kinda neat effect.
MPC-Live/Remix16