Why do some people put one airbag on the rear passenger wheel? Why wouldn't you do it on both sides. I think it has something to do with how the DS turns. What is the reason to do this.

Do they have a switch inside so you can control ride height or is it an automatic system?

 

The reason for 1 air bag on the passenger side is because the way the body torques when you launch. Ever watch a car launch at the strip from behind? The drivers side will torque upwards as the motor is causing this. The reason for the air bag is to compensate for the body roll of the torque to keep the rear tires equally weighted.