Both AI chats have a thinking choice beside their send button. It's remembered on each device.
Fast: quick answers, in a few seconds. Good for simple questions and small edits.
Balanced (the default): thinks it through and can take more steps, like looking up several notes before answering.
Deep: takes longer, for hard questions, plans and comparisons across many notes.
Balanced and Deep can take up to a few minutes; the chat shows "Thinking…" with the seconds so far. Each answer counts as one AI request, whichever you pick.