Are all matchmaker clamps the same? I want to use my right hand GX 11 speed shifter with SRAM guide brakes…….

The MM attachment is the same for all SRAM shifters, as far as I know. The clamp comes with the brake, so you shouldn’t have any issues.
It is only the Reverb remote that has its own clamp, which replaces the one shipped with the brake lever.

l.e. Apparently the brakes don’t have the shifter attachment, that needs to be purchased separately together with a new clamp: http://www.chainreactioncycles.com/ro/en/avid-matchmaker-x/rp-prod40907