Use Cmd+K when: you know exactly what to change and it's in one place.
Use Cmd+L when: you're exploring, learning, or need to think through options.
Use Cmd+I when: the change spans multiple files or you want the AI to plan the approach.
Starting with the wrong mode wastes time. Cmd+K for a multi-file refactor will frustrate you. Composer for a one-line fix is overkill.