What Chat Mode is best to use to

it depends. Usually an agent will get best accuracy if you craft the tool descriptions nicely. Context chat engine is probably the fastest

I'm using with Claude LLM, and basically I need to chat/ask question base on documents. what option will have better results and less hallucination ? Normal QA is not providing good results and I'm hoping with chat to be able to refine result with additional guidance on chat and base on the history to provide better response