Do I need regen, and how much?

It's a matter of taste.

• Motocross: many run 0–30%. With strong regen the front dives when you close the throttle, and in the wet the rear wheel can try to overtake the front.
• Woods and descents: regen helps engine-brake and adds a little charge (a long descent gave back 4%).
• Long races: from 20% is recommended to save energy.