Is it possible to set microphone sound to not be output from the [BOOTH] output terminals?

Yes. Follow the procedure below to configure the setting.

1) Connect this unit to your computer via a USB cable.

2) Launch rekordbox.

3) Open [Preferences] of rekordbox.

4) Select the controller.

5) Select the [MIXER] tab.

6) Select the [Does not output microphone sound to the Booth output.] check box in the Booth output settings.