On my '05 Prius there is a quick electric noise, but not a "bark" when I step on the brake. My '16 Prius doesn't have any noise. I'm pretty sure that if you are not tracking the car (I don't recommend it), you shouldn't worry about brake cooling. The covers can reduce brake dust. I don't think regenerative brakes heat up like friction brakes do. Your Lexus has both types of brakes. You probably won't have to change the brake pads until 200k miles like me.