People have been overclocking monitors for years, its' nothing new. I think its very important to point out these though :
1) Just because your monitor is capable of refreshing at 75 (or whatever the OC is)
doesnt mean it can do it reliably to show all frames. Sometime's frames will skip or you might encounter judder here and there. This means the refresh rate might be too high and its advisable to drop abit lower. You can always use the UFO test here to check it -
https://www.testufo.com/frameskipping.
---- Another really important thing about this is also not to confuse judder from any smoothing you've enabled on your TV with the new refresh rate (I have this on my old 2016 4K TV). Its best to disable any motion smoothing (Or whatever your TV has) so you're sure the OC is working properly.
2) Alot of monitor's will lose contrast saturation when you overclock,
there is no way to counteract this afaik. My last two screens were both overclocked and on the 1080p VA panel i lost about 1/3rd of my contrast. On My current 4K TV i can go to 73hz at 1080p but colours are much dimmer and blacks are not really black anymore. So this is also one side effect.
Some montor's don't get affected by this at all.
3)
If you haven't tried it yet - you're loosing out. It can be really worth it to OC. You never know what your screen might be capable off, but please always read guides/tutorials thoroughly.
My preferred way to test OC'ing : is to remote desktop to the machine from another computer. Start off small so it works - Use CRU to adjust as you go and after you have restarted the display (Using CRU restart exe) - wait for the display to come back up. Since you're still logged in from the remote machine, all you should see is the lock screen.
If it doesnt - you've gone too far, but If it does - Congrats - you're one hz higher than you were before. Simply back down the hz and restart again to fix.