In fact all you need is the most extreme depth with vary power. White will not leave a mark and black will go that extreme depth. The gradient will go to everything in between. Even engraving top to bottom of the total half inch range I would defy you to define two different shades next to each (123vs124) I have tried to work with images with not enough shades available and even if you use the contrast you get the “rice terraces” effect as shades are 30 or 40 numbers apart but in practice you adjust the contrast to be at each extreme without to many levels at at either black or white. If you can see the details they will show up.
If you want to get good master files you can make one set for each material like this one…
Then with a max of two or three materials representing a range of basswood to walnut all 3/8 thick do a range of speeds from 4000 to 1000 with a few LPI from 1355 to 340 full power and single depth and perhaps the same with the dithered choice.
From such a set you could easily windage the ideal settings for just about anything.