Here is an explanation of the INFJ balance (or reflectivity) I was talking about:
"when the INFJ communicates a joyful experience to someone, and that person has a positive response, the INFJ will pick up on that positive emotional energy using their Se and Fe, and thus reinforce the already positive state of mind, like throwing oil onto fire..."
INFJ Strategies for Dealing with Emotions: Part II: Protecting Positive Emotions
As for INFPs being intense: doesn't happen. INFPs don't whip their emotions into an intense feverish state, but prefer mellow emotional states.