There are separate regen options for throttle off and braking regen so the default is 100% braking regen but could be lowered for some unknown reason.
IIRC, the sport mode only has deceleration regen and no braking regen. But I set my custom mode for almost the opposite, 100% braking regen and almost no deceleration regen. Works better for higher speeds to be able to coast better. But when you must slow down, might as well have all the regen you can get. And more regen on braking should save the brake wear by quite a bit.
But with the brake light, I was only mentioning the brake regen, of course. I think all it does is let the deceleration regen go to more regen while braking, by using the juice for the brake light as a trigger. I figure they both do the same thing, work the same way, but the percentages can be set independently from each other.
-Don- Reno, NV