The left paddle adjusts the amount of regen that is active up to 0.6g and the right paddle adjusts the maximum torque available so you can “downshift” on the way into a corner and “upshift” on the way out. I don’t see how it’s better than using your right foot, but supposedly it is pretty intuitive.
Some EVs use them to let the driver change the "drag" of the electric motors. Imagine the "L" (sometimes "B") position of automatic gear but with finer control than all-or-nothing.