Default Questions on Undervolting and Frequencies.

Hello,
Wondering if someone could help me. I am trying to optimise my battery usage to get the most out of my phone without affecting much functionality. To that end, I use Greenify and Xposed modules like recent apps cleaner.

Yesterday I was playing with undervolting using Rom Toolbox pro. I undervolted all cores by 75mV each.
After that i started playing Real Racing 3 to check if the phone was still operating smoothly. The game froze , so i closed it and checked the CPU states to see which frequency the game was running on most.

I found out that, most of the time, real racing 3 operates at a maximum of 1400 MHz frequency, no more. I then increased the voltage of 1200, 1400 and 1600 Mhz cores by 25 mV each. Again I played real racing 3. This time the game ran smoothly, but afterwards, when i checked the CPU stats again, i saw that the game was now also using 1600 Mhz and 1900 Mhz (for a very few seconds out of the 7 minutes i played it) frequencies.

So my question is:
If we undervolt the phone, would it simply make applications use higher frequencies so that they get their required voltage?
If they use higher frequencies on an undervolted phone, will it have any adverse effect on battery life as compared to using original frequency at original voltage?
What would be the best way to control this situation so that i can undervolt my phone for normal use, but use higher voltages when running certain apps? Xposed modules like per app performance controls only allows us to change the frequencies and governors per app, not the kernel voltage.

thanks for reading and hope there is someone here who can teach me on how to control my voltages better.

cheers!
Primary Device :
Samsung Galaxy Note 3 SM-N900 (Exynos)
Rooted,
Criskelo Rom
Halazsk Kernel.
Warranty - VOID

Secondary Device :
Notion Ink Adam Tablet
10.1 inch.
Rooted
Cyanogen mod 10.1 (Jellybean 4.3)