Well if it matters to anyone, my friend has a $3000 2013 MBP with Retina display, and he installed Windows 7 onto it and "played" Bioshock Infinite on it at full resolution (2880x1800) and while it LOOKED very nice, he got only about 7-12 FPS (max settings, AA off (cause at that res on 15" screen, why AA?)) which was laughable.. His MBP had a 550M gpu and 3rd gen i7 processor, and the game got a more reasonable framerate at 1080p.
I have zero doubts this laptop would have ANY issue with ANY other type of activity on a 4K display, considering his MBP (less in means of power than any model G750) can do ANYTHING else at "retina" resolution, aside from games like Bioshock Infinite.
Things like Photoshop, internet browsing, 4K movies shouldn't be an issue on this machine. But that's just my guess.
Asus G750JW-DB71