What movement speeds are you getting out of your CNC and how deep are you planning to cut?
Any should work for light engraving, but if you're wanting to cut deeper you're going to need a bigger router. I've had good luck using a roto-zip cutting oak and popular, but my dremel would burn the wood (even on soft wood) and the bit due to the high speeds and quality of the bits.
A roto-zip is much lighter than a full size router, but still able to allow use of 1/4" router bits.
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