So your mostly fighting against wattage used and temperature verses clock , undervolting mine i started at 1.1V Gpu core Volts and 1500 with stock memory clocks and worked up until it crashed at about 1550 , checked temps ,especially hotspot temp in hwinfo64 under heavy load and decided i could go higher so with a max of 1.16 volts ,stock memory clock, i can run it very stable at 1660.
you can overclock the memory a bit with little gains in fps tbh but large gains in heat output beyond 950 ,this heat output and the added wattage pulled (from the total allowed remember) limits the cores top clock holding stability in some scenarios unless that is you max the power slider , which again adds heat and reduces the time at top clock.
all in for games leave memory as is and the wattage and heat saved will allow you to run your core higher at a lower voltage(volts scale up marginally with heat) , start at 1.1 1500 and run a windowed 3d load then up it in 25Mhz steps , when it crashes add volts in .1 steps or drop clocks
