And that's an impossible thing to answer. First – What is BEST? Is that the overclock that gives you the highest hash rate? Or could it be the highest efficiency? Or the most heat in a cold winter?

So with some basic knowledge of how to optimize the overclock on your own, you can use our examples as a starting point and then do the fine-tuning yourself to succeed in what your goal is with the overclock!
This article will cover Nvidia cards, where there are some basic rules when mining algorithms where memory usage is (close to) zero, and the core is all that matters.

Usable for coins such as:
Alephium (ALPH)
Kaspa (KAS)
Radiant (RXD)
First, we want to lock the memory to 810 MHz. Since the algorithm does not use any memory, we will turn the memory down to save power (and generate less heat). Some mining OS lets you do this in the overclock panel, while miners like lolMiner let you do this in the miner options.

--mclk 810
Second, we want to add a locked core to both limits the power usage and to be able to set a core offset later. For most NVidia Amperes (3000 series), you will find the highest efficiency around 1305-1500 core clock. If you want a higher hash rate, the higher the locked core, the higher the hash rate. This can either be set in the mining OS or directly into the miner options:

--cclk 1455
Third, we want to add some core offset. The core will still run at the locked core value, but with the added offset, the GPU will run at a lower voltage and save power. The higher the core offset, the lower power and higher the efficiency. Most Ampere GPUs can handle around 200-400 offset. If core offsets are set too high, the GPU will crash. This can value can also be set in lolMiner*

--coff 250

* Needs NVidia driver version 520 or later to work! You also need to run the miner with root/admin privileges