Who can really say? There's far too few samples(games). There's no one size fits all application here... but if Ark is all you play, then I guess it's ok, but still...
Fluctuations in core clock should be expected, and with how the built in Gpu Boost works, it's nigh impossible to sustain a 'stable frequency' across several different applications; 'cause the moment the frequency does change, you'll then be led to think it unstable and have to start all over...
Besides, it's meant to overclock as high as it can until it runs into a limit.
"NVIDIA's dynamic overclocking mechanism, GPU Boost 4.0, dynamically adjusts clock and voltage based factors such as render load, temperature, and power, to deliver max performance." No real input from the end user necessary.
KFA2 2060 is one of several models with a low total board power limit of 160w compared to some other 2060 models. Even the 2060 FE has a max of 190w. The vendor probably isn't too confident with the cooler they used, or they cut corners with the power delivery to lower the cost of the product. In other words, this model's boost curves won't go as high as others.