hat - chat directly, character card is your prompt
instruct- chat between "you" and "assistant" using the model's prompt format
chat-instruct- chat with you and a character card as a prompt but with the instruct template applied. .i.e "you are an AI playing x character, respond as the character would" converted to alpaca, wizard or whatever
There is no best, but for factual information, you probably want to keep to instruct mode. instruct-chat doesn't necessarily play the characters better or make them write longer. It's sort of hit or miss. one may work better than the other for a particular model and prompt.