Just a small update:

The GRBL fork does work nice. The one axis sinker/drill part gives a stable burn and the first test with the x axis wasn't bad.

I'm still testing different ways for the XY motion. The one shown in the video stops the XY motion while the Z axis is adjusting.

The workpiece was clamped down very sloppy. With a solid vice this would have been a different quality. Lots of room to improve but all in all a very nice first cut.

I also had to stop the process since the workpiece was on the bottom of the plastic container and the electrode started scratching the plastic.