Look I am just going towards the safe side here.
No matter even if a game runs at 500 FPS, you would see only 60 FPS in your monitor. Anything higher than that would be cancelled because 95% of the monitors used by people operate at 60 Hz and the rest 5% at 120 Hz. This means that a monitor will either refresh its screen 60 times in 1 second (That means 60 Frames Per Second, Nothing higher than that) or 120 times.
In the latter case you need a 120 Hz monitor to see the smoothness shown by your card. If you have a 60 Hz monitor, your experience would be exactly same no matter the FPS as long as it stays higher than 60 FPS. Two GTX 770s have hell a lot of power. They do not need to be overclocked for any possible reason.
One more thing, 60 FPS is very very smooth and you literally do not need anything smoother than that. People overclock their cards because they see lag, etc. If there is no lag while playing and its buttery smooth, no need to OC and test you card's limits. Stay on the safe side and you would be fine. No need to take chances and get higher clock speeds. ^^