The Volume Control Box and the Volume Switch - two devices to control volume with different usecases.
The Volume Control Box is intented to be used in your amps FX-loop. It controls the volume without altering your sound and your amp's distortion level. For distorted amp sounds at bedroom levels!
The Volume Switch is best used as the first pedal in your chain (or somewhere else in front of your amp).
It can reduce your guitars volume level - similar to your guitar's volume knob, but without altering the sound of the guitar and without steeling treble.
The reduced volume level reduces the amp-distortion, so you can basically add another channel to your amp with the Volume Switch!