Keith,
Yes, I fly my GT2 at 200mw. Your bird may have the SP3 which has a 25, 200, 600mw VTX in it. I'm not sure that it'll have a great impact on your battery but it will produce more heat. I'd try 200 if you don't feel you're getting good enough range bump it to 600. It's the strength that the VTX is outputting to your goggles. It has nothing to do with the radio.
Jerry