Hi Davideast31!
My english isn´t the best so i will keep my answer short
Your CDJs act like a USB Soundinterface.
So you are able to send the CD signal to Mixvibes (USB) and
to play out (RCA) the sound from Mixvibes.
Now you have different options to do this:
With External Mixer:(like in your link)
Mixvibes Player1/2 is controlled by CDJ1/2 -> via RCA-cable to Mixer

Monitoring (Headphones) done by Mixer

Sound control done by mixer
With External Mixer A:Mixvibes Player1/2 is controlled by CDJ1/2 AND
Internal MixVibes mixer is controlled by CDJ1/2 via MIDI.
One CDJ acts as MasterOutput the other one as Headphone Output for playing back the sound from MixVibes.

Monitoring (Headphones) done by Mixvibes

Sound control done by MixVibes
May this helps you...
Best regards Marxon
Just for completeness:
If you want to play Audio CDs just push the "Bypass" button,
Mixvibes then gives out Sound comming from your CDjs.