Since you're running Mach3, you'll probably need the PicConvert module from JTech (https://jtechphotonics.com/?product=dacpwm-converter-board). Mach3 tends to pause between operations on rastering, so it will just turn everything black rather than changing the intensity of the laser. This module converts what would be Z axis movement into PWM for the laser.
I kinda agree with you Leo. I don't really need the laser on the cnc, maybe for adding some branding, labeling, or instructions as part of a finish would be nice, but not for doing images/engraving. I think the one thing that would be intriguing is the preview of a lasered item in Vectric and to get a baseline for laser intensity.