No issues, had I got shallower the amount of (or lack) pigment would make it shine through - which could if done correctly become a very cool feature…
1/16" was deep enough for the blacks to be real black.
You could remount the board onto the CNC and skim most of it off prior to sanding it down. For one-offs the sanding by hand is acceptable, if I were to make business of it a planar sander would make sense.
When wet sanding you can go through the epoxy real quick using 120/240grit, then finish it off with 400/800.