How do I compare monitor gammas?

[Yo Whats Up]

So, I overclocked my monitor from 60hz to 75hz, at 76 it says input not supported. Do you think it's a good idea to keep it at 74hz just in case, so I can have 1hz of safety, just like you generally want to have some free space in front of your toes when buying shoes and not buy ones that are sticking exactly to your toes like glue? Just so I can be sure my monitor is not at the limit of its capabilities of 75hz? Or is 75hz fine? Which brings me to my other question, is overclocking safe? Are there any negative effects?

 

And now to my main question: in the intel hd graphics settings, the gamma is set by default at 1.0, and can be changed in 0.1 intervals. At 1.0 it looks good, although at 1.1 it looks good too. 1.2 and above is too bright, and 0.9 and below is too dark. So at 0.9 and below and 1.2 and above I can definitely tell it's too dark/bright, but between 1.0 and 1.1 I can't tell which is which if I look away for a few seconds and they're scrambled. When I switch from 60 hz to anything above 60hz, the gamma of my monitor is hiddenly decreased by either 0.1 or 0.2. Meaning, in the graphics settings it still shows 1.0, but I can clearly see it's darker. Now the problem is, since there are TWO gamma settings at 60hz where the gamma looks good to me, 1.0 and 1.1, when I switch to 74/75hz, I'm not sure if 1.1 or 1.2 gamma at 74/75hz is the corresponding gamma to 1.0 at 60 hz, since both values look good to me. 1.3 gamma at 74/75hz already looks kinda bright, just like 1.2 gamma does at 60hz, but I feel like 1.2 gamma at 60hz looks slightly brighter than 1.3 at 74/75hz, or that could be just me. I want to be able to compare the two gammas side by side so I can find which value, 1.1 or 1.2 gamma at 74/75hz, is the equivalent value of 1.0 gamma at 60hz. I tried taking screenshots with my phone, but my phone camera is not good enough to distinguish such a small gamma change. The difference of 0.1 gamma is not small enough for it not to matter but not big enough so that I can easily remember it when comparing two good looking gamma values, there's no way to change both refresh rate and gamma at the same time, so I have to first change one and then change the other, and even if there was, it takes about 5 seconds for the refresh rate to change during which my screen is black, so by that time I've already forgotten how the colors exactly looked and that's enough for me not to be able to distinguish between the two gamma values. So how can I somehow compare them to be able to find the REAL gamma value, the one I've been using for years with this monitor? Yes both look good enough for me to use either, but this gamma color holds a special place in my heart so I want to make sure I'm using it rather than 0.1 lower/higher gamma which still looks good