On the pro models the controller only sends on/off commands to the laser driver so changing spindle speed has no effect, but not sure if the elite has the same controller although it does look the same in the pics ( talking about the computer box not the handheld part).
Step over is the most critical setting I have found and it has to be set correctly in 2 places. In the tool data base bit size should be .012 inches or .304mm if using metric with 100% step over. Then when creating the quick engrave toolpath in your Vectric software just below the depth/pressure that should be .001 inches there is another step over box where you set the outline/fill option. This should be .012 inches or .304mm also or the laser doesn’t step far enough and will cause charring and be very dark and deep with burnover.
As far as changing laser power there are pins in the laser driver under the fan, with all 4 attached the laser is 4.2w, remove one and it drops to 3.8w and so on. I have not had to try this and get perfect burns as long as I have the step over set correctly.