Press the Windows + R key combination to open the Run command box. Type cmd and press Enter. When the Command Prompt opens, type slmgr -dli and press Enter. A Windows Script Host Dialogue box will appear with some information about your operating system, including the license type of Windows 10
Pascal and Turing boost higher the lower temps are, for the absolute best perf you want to keep it below 55C, most air coolers won't do that without maxed fans and a lot of noise. So people usually compromise and let it run slightly hotter. Up to 75C is fine, 80C is getting a bit hot, 90C is too hot (should keep it below 85C at all times). If you have reasonable airflow and set a proper fan profile (stock ones are usually garbage) you should easily be able to keep it at around 75C. 2060s aren't hot GPUs in the first place so they don't take a lot to cool, even a small cooler like this should handle it.