Do you know if your games are cpu limited or graphics limited?
You could buy your new game and find out then.
Or, you could do some tests now:
Some games are graphics limited like fast action shooters.
Others are cpu core speed limited like strategy, sims, and mmo.
Multiplayer with many participants tend to like many threads.
You need to find out which.
------------------------------------------------------------
To help clarify your CPU/GPU options, run these two tests:
a) Run YOUR games, but lower your resolution and eye candy.
If your FPS increases, it indicates that your cpu is strong enough to drive a better graphics configuration.
If your FPS stays the same, you are likely more cpu limited.
b) Limit your cpu, either by reducing the OC, or, in windows power management, limit the maximum cpu% to something like 70%.
Go to control panel/power options/change plan settings/change advanced power settings/processor power management/maximum processor state/
This will simulate what a lack of cpu power will do.
Conversely what a 30% improvement in core speed might do.
If you want to go to a 7 series kaby lake cpu, you will need to check the bios level of your H110 motherboard and update it using your current 6 series cpu.
The big plus of a i7-7700K is that it runs stock at a good clock rate of 4.2.
No overclocking is really necessary.