

Your average woodworking router is already running at something like 20k RPM for ~6mm and larger bits. High speed should do fine on wood, at whatever feed rate doesn’t burn it. Maybe just use light passes to save your endmills.
That said, I am most assuredly NOT a CNC machinist, just a nerd with woodworking tools and a couple of low end maker devices that run gcode.
I’ve had a scalp biopsy before. The specific spot they cut will have a scar and if it’s a large area and you keep your hair extremely short, then you might be able to spot the specific spot, but generally speaking, no. It won’t case hair loss. I honestly don’t even remember where they cut me. They should also give you a little shot of numbing agent, so it shouldn’t hurt much at all during and then afterwards it’s just like any other incision.
No biggie, and generally always well worth it if your doctor thinks they seem something worth cutting off.