In Fl we can have 2 different grades. Driver & passenger doors have to be a certain (lighter) level, the qtr and rear windows can be darker. I just tint mine the door level all around because I don't like the 2 shade look.
I will say this. If you ever worked as an officer and approached a vehicle, you would want to see inside of it too.
Light travels faster than sound. This is why some people appear bright until you hear them speak.