Everything in the Vectric software can be defined in inches (Imperial) or Metric. The software will convert, as needed, to what your post processor requires. I work 99% of the time in Imperial, but my tools are defined in both Imperial and metric. If I have a 3mm bit, I define it as 3mm. I always define my feed rates as Imperial (in/min), because that's what I've tested.
The bottom line is that you only have to talk metric to your Axiom when you enter numbers into your handheld. It only knows metric; Distances, puck thickness, are all in metric.