Sorry, I neglected your other question. The difference between knobs and buttons are:
A knob allows you to move anywhere between the minimum and maximum of the "learned" parameters that are connected.
A button toggles between the 2 states: Minimum and Maximum. This allows you to assign to, say, BREVERB's "Wet" control. Set min on a button to 0, and set max on that button to your preferred setting. This will cause the button to sort of behave like a "reverb on/off" button.