As it has been mentioned many times in the direct ones, such low response times are almost totally unnoticeable so don't worry so much about those details, but answering your question for what I have found so quickly:
mprt is "Moving Picture Response Time"
gtg is "Gray to Gray" (or transition of the pixel from gray to gray) the time it takes for the pixel to go from gray to off and back to that gray.
If you want a fast gaming monitor, one with a TN panel is recommended, it has many disadvantages in terms of quality, but in terms of response it is better than IPS

Good,

I'm from Warface in case you want to play...

My nick is the one I have on the forum.