If i have larger knowledge base, was AI answering question more costly (higher AI-spend) ? or it is the same?

it will indeed increase the cost as the size of your KB scales

So it will increase but not that significant? Also how do I change the model? Is it possible to use another model other than from openai gpt (like llama or maybe llm model from hugging face). Really appreciate your answer, thankss

you can change the model in the settings for your Knowledge Agent in the studio