It will change both outputs,As long as bothyou don't use the samePWM (singlei.e. analogWrite) timeron pin 9, any changes made to timer1 won't affect pin 9.
But you can use code to convert a 8-bit PWM value to a 16-bit value by simply multiplying the 8-bit value by 256.
But you can use code to convert a 8-bit PWM value to a 16-bit value by simply multiplying the 8-bit value by 256.