The EXP will only change the resoponce os the servo, the speed stays the same, Picture a diagnal line on a 45degree angle. Then make it curve up or down, that is what is happening to the steering responce. The 3PK actually shows this as a graph when u make the EXP adjustments
The DUAL RATE on the thumb wheel is only going to limit your steering throw. It simultaniously reduce max through of left and right at the same time. So from 100% steering throw down to 0% as you adjust the wheel. IT will not likely take the twitchy ness out of your steering but it will take out some steering if your over cranking the wheel in the corners and find your oversteering. ITs handy if you can control your wrist!