INFJ vs INFP empathy - How they read and understand people.
You may already know that INFJs and INFPs are the deepest-empathetic MBTI types (in consensus). However, it's often this fact causes INFJ/INFPs to mistype as each other.
It isn't false though! Many healthy INFJs and INFPs are very empathetic/analytic towards people. But here's a catch: They express/acknowledge feelings and empathy very differently, believe it or not.
So, this post will be dedicated to distinguishing the two:
1. INFJ vs INFP in Reading people
The function stack for INFJ is Dominant Ni (Introverted Intuiton) - Auxillary Fe (Extraverted Feeling) - Tertiary Ti (Introverted Thinking) - Inferior Se (Extraverted Sensing).
Meanwhile, INFP is Dominant Fi (Introverted Feeling) - Auxillary Ne (Extraverted Intuition) - Tertiary Si (Introverted Sensing) - Inferior Te (Extraverted Thinking).
For those newer to the cognitive functions side, you may be surprised at how different the stacks are despite a one letter difference (J/P). But don't shit your pants yet! I will explain how this works when reading people.
INFJ
Healthy use of INFJ's Fe allows their Ni-Ti to focus attention on people - in which Ni-Ti subconsciously exchanges ideas/details/questions about the person they're looking at. If Inferior Se is developed well, the INFJ may include Se in the analysis, helping them keep to the present, pick up body language, signals, social cues, etc. -- Then, their Ni organizes all the information (including seemingly irrelevant details), and constructs it into their "picture" (or "web") of what this person is like. In some cases (maybe in type 4s or even 5s), this can lead to over-idealization of someone, and soon disappointment when the INFJ meets who they truly are.
Subconsciously, INFJs allow room for possibility, as they constantly gather info about the person on the flow (even the tiniest details), or even information from irrelevant events that may strike the INFJs perspective on how they analyze people. This allows them to mentally prepare (if consciously) for unexpected events/information about the person to be thrown at them (can't say this'll stop them from being surprised though).
In more unhealthy cases, INFJs may easily close off their flexibility in analyzing people - they can be prone to indulging in Ni-Fe, leading to quicker and harsher judgements (even black-and-white thinking) using what could be stereotypes, or "social norms" -- which in turn, causes them to appear delusional or narrow-minded.
INFP
Their main way of analysing/empathizing with people would be through the "mirroring method" (Fi-Si). This allows for them to pick up patterns/"feeling cues" in people (Aux Ne), and compare them through their Fi-Si (reflection of self and past), which then Ne will jump in to expand on it. The process probably goes something like:
"Ugh, this person is so annoying to me!" Suddenly thinks of how they acted like that in the past (Fi-Si) "Aww, this person is just going through that phase. They still have a lot to learn!" Suddenly connects other information/irrelevant details about what they were like in that phase (Ne) "I wonder if this person could be one of those people? I wonder if they're just like me? If so, I wonder if I could have a deep relationship with them? - Maybe I could fix them!" Probably starts to imagine scenarios of their future relationship (Fi-Ne)
Of course, not all INFPs would have this exact thought process (It may only ring true for 4w5s). Some may even do it in different orders, or would think about it in different emotions/thoughts.
It's likely this is the reason Fi-doms are amazing at detecting their own (mostly by gut instinct), whether it'd be through the "vibes" or "fashion" of someone. To add, INFPs (due to their Fi) are capable of "feeling hyperspecifically", and zone in on the individual feelings of someone to empathize/relate.
In more unhealthy cases, like INFJs, INFPs can get delusional and narrow-minded in how they analyse people, - maybe even too reflective of their own feelings, experience, and ideas. As a result, INFPs can have a hard time grasping that other people don't share the same morals, values, or reactions to situations as them, and may feel that others are just "lost" or haven't "seen everything".
2. INFJ vs INFP in fixing people
Though not heavily debated, people are confused whether INFJs are better than INFPs (or vice versa) in the therapeutic realm. In my opinion, I feel like they're both {possibly} equals, just both are better at specific situations than the other.
Of course, that's not to say INFJ/INFP can only do this and the other can't. I believe they're stronger/comfortable at one thing than the other, and they could even be partners in crime.
INFJ
Their main way of empathy is through their Ni-Fe. Unlike the INFP, INFJ's only proper "mirroring method" would be through their Tert Ti (or Ni-Ti, depending on the situation) - since Ti is the only subjective function they're aware of (which in turn, makes them subconsciously assume everyone has the same way of problem solving, deduction methods, or logical takes as them)
The INFJ's Fe will enable their interest in the situation. They'll more-ly concern themselves on the thought-processing of this person: "Why exactly does this person think/feel that way?" -> "Why did this event cause the person to react this way?" -> "Why did this event happen?" -> "Why did this person react like that then" -> and etc. After INFJ is comfortable with the answers they retrieved from their little silly interrogation, their Ni-Ti will allow them to re-visualize the whole situation (identifying the root/core of the problem, then trying to think of solutions)
Because of this, INFJs are much more effective in dealing with people's ego problems, poor judgements, problematic ideals/perspectives/beliefs, and miscommunications between relationships -- since they can dig into your subconscious and core motives, revealing insights and perspectives unexpected by the person.
INFP
Their way of fixing problems would be much more flexible compared to an INFJ. We can thank their instinctual mirroring method Fi (or Fi-Si).
Fi in general is what keeps the INFP tune in with themselves, aware of what ticks or emotionally damages them, and what their values are (what drives them to fulfill their lives - at least true in type 4 INFPs). If used in a healthy manner, the INFP could actually reflect themselves into other people - to get an idea of what ticks others, what could annoy or make others happy, and can learn what to do or don't (all based on how they feel).
While this style of feeling is subjective... Compared to Fe, it's rather hyperspecific (as they can feel deeply - though it can depend on who or what the situation is). Not to mention, their Ne (which works in several ways) will extract/connect tons of other details/seemingly irrelevant information from their Fi-Si, and apply it to what this person could be feeling, or what they might be going through (Sometimes even generate ideas on how to comfort the person).
That's why many healthy INFPs are excellent at dealing with more emotional problems: like comforting for someone who feels hopeless or empty inside, or is suffering from a mental disorder. The INFP will be there to deeply understand how they feel, and there to assure others that they're not alone.