I believe the 2700x Turbos to 4.3ghz on 1 core right?
Overclocking the cpu affects all cores so. Would an ALL core OC at 4ghz perform better?
It also depends on what your doing if your gaming a 4.3Ghz on 1 core would probably be slightly better than an all core oc to 4Ghz. Because games don't usually use more than one or two cores. If your doing video editing or something more professional then you might benefit more from a 4Ghz OC on all cores.
Even a 4.2ghz on all cores isn't much of a difference from stock speeds and often falls behind.
You can find 4ghz numbers in their 2700 review and they are not pretty in comparison.
Just run that processor at stock and get a better air cooler if you want.
If you want a faster running processor out of the box and you still wanna OC to have some fun with it, get an i7-8700K.
Costs only 70 bucks more and worth the trouble if you main goal is gaming.