Overclocking will get you a lot more heat.
MSI afterburner can't overclock ( at least the legit versions for laptop can't, with the newest nvidia drivers ).
But there are some asus versions of GPU clock for laptops, that are safe to use to overclock just a little bit. ( you just push a button and it's stable +5% overclock or something like that ). You can go for more overclock with some older versions of graphics drivers and msi or other programs...but I don't recomend it, because...why try your luck. Just stick to newest graphics drivers. If you realy have the need to overclock, do it on your cpu with intel xtu, just raise the multipliers on cores and cache.
In 3d mark firestrike you should be getting around 8500 points.
I would sugest you use undervolt in intel xtu program. You can read about it in every high temperature post. It won't hurt performance, and will reduce your temperatures by 3-5 degrees.
Also if you don't like your temperatures, download NotebookFanControl, and use the uploaded Silent profile for G751JY.
I can't recomend it enough, it's reduces temps by almost 10 degrees for me.
You realy don't need to overclock for any game yet, but if you will overclock you should use the fan profile and the undervolt ( also update BIOS is a must ).