1) Creep, Roll, and Hold do not have anything to do with Regen. The Creep, Roll and Hold have to do with how the vehicle stops at the last or holds in place once stopped. Creep, is like a current ICE automatic transmission, if you let of the brake the car would creep forward. Roll, means at the last of the stopping <4mph the vehicle would then need the brakes applied to come to a full stop. Hold, means that the vehicle will stay in place once it comes to a complete stop regen all the way to stop (<4mph).
2) Yes, You can configure Sexy Buttons to adjust the amount of regen with a press of a button. I have a button for this, but honestly only use it when it's really Icy or snowy on the roads.
3) Again those settings don't affect regen at all. You will always have regen on unless you use Sexy Buttons to override it.
Hope that helps