Should I try 1 or 2 tips, and 200 or 400 pulses of eMatrix for my shallow, moderate boxcar scars?

The number of tips and pulses depends on the size of the treatment area, and the amount of overlap of pulses (for acne scarring more overlap will generally give better results). It is hard to know exactly how many pulses it will take until you see the patient and start the procedure, but I usually use 150-200 pulses for one full face treatment, without a lot of overlap. You will likely need 2-4 treatments. I don't charge by the number of pulses, but if you can get a better deal by "buying" more pulses, then go with the higher number.

You should see the video below. I like eMatrix, and it works very well for early and mild to moderate scars. Like you said best for shallow box car scars. There are better treatments out there, but I still use this device. The outcome will depend on the power settings, how accurate your Specialist is at delivering the pulses, and the overlap. All explained in the video link. CheersDr Davin Lim Laser and aesthetic dermatologistBrisbane. Australia.