Its not the Gsync I would be worrying about. or the 165Hz refresh rate of this monitor or the display port cable.
Its the task you are asking of a GTX970M with 3GB VRAM in driving a 2K display.
The G751JT struggles with a 1920x1080 display, I'm not so sure you will like the results of an overheated slow FPS GPU @ 2560 x 1440. Thats a jump from 2 million pixels to 3.7 million pixel or almost double.