In short: yes. You can tune these values when self hosting - it basically changes the b chance which tokens will be used under which circumstances.

Like Scipitie said, sort of.

In the ChatGPT app, there's tons of shuffling in the background, like context being injected, maybe sampling changed, agenic action, quantization... its "far" from the actual LLM, opaque by design, and as a result certainly not deterministic.

You can sometimes get deterministic output with the OpenAI API, but it's also dependent on nothing changing on their end. And their end changes a lot.

But self hosting or using a more consistent provider will give you deterministic output.