There are two separate things: ChatGPT, and the API for accessing AI models via software.
ChatGPT, the website, doesn’t let us know the settings they use and there is no hack way of discovering it (although one could do statistical analysis over hundreds of the same session).
The setting of ChatGPT is likely similar to recommendations seen in various documentation: temperature=0.7, top-p=1.0 (default, no limitation). The top-k is likely unset, meaning all 100k tokens are considered.