I would not worry about setting it manually right now. You should not NEED to overclock that CPU to get terrific performance without any overclock at all. You can worry about overclocking after you get the temperatures down to an acceptable level and see if they stay there during the same kind of gaming loads that had it overheating while overclocked.
That CPU is only two generations old, being from the Skylake family. It has 8 cores and 16 threads, and at stock speeds already has a 3.6Ghz base clock with a 4.3Ghz turbo speed, which means it's a MONSTER CPU and with all those cores, if you overclock, it's going to take a custom cooling loop to keep it cool, not an all in one closed loop cooler like the H115i. That's a very good cooler, for an All in One closed loop, but it's only good for cooling maybe up to six cores/12 thread processors if you're overclocking and even then probably only for an average overclock, not a major overclock.
I would suggest that you go into your BIOS, make sure you are in the advanced mode, not the EZ mode, then click on the Exit menu, select "Load optimized defaults", click save, then exit and reboot. Once you are back in windows after setting the bios back to it's default values, go try those games again and see what your temperatures are like. If they are good now, THEN we can worry about trying to do a LITTLE bit of overclocking, but you will not want to get carried away with overclocking on this system because with an 8/16 core CPU, anything over stock settings is instantly going to create a lot more heat than CPU's like the i7 with fewer cores does when overclocked.
I would also SERIOUSLY consider getting two high quality 140mm fans and installing them in the TOP of the case as additional exhaust fans. One exhaust fan on the back is not enough to relieve the pressure from those three front intake fans, even though they are going through a radiator. You are making the front fans work too hard, against too much inside pressure, and you can help them out AND also get other heat out of the case by putting a couple of 140, or even 120mm, fans up in the top for extra exhaust blowing OUT of the case.