If you want to know the settings Mike used, only Mike can tell you. 
ButâŚI would start with Draft Photo settings and work from there.
Draft Photo works great for photos. Very important to clean up the image as much as possible, and bump the contrast first, in some kind of raster software. (Photoshop or GIMP).
@jbmanning5 has a great Action written (for sale) for Photoshop if you have thatâŚpractically âone click easyâ cleanup and contrast to make your engrave results pop.
Or you can read how to do it yourself here:
https://glowforge.com/support/topic/first-three-prints/Prep%20a%20Photo%20Engrave%20with%20Gimp