I’ll gladly give it a try, from what I’ve observed! I love these two types so much and everything gets magical around them, so I’m sorry if I become too personal and symbolic with my descriptions! (and I’ll try a similar format, I suppose?)
Both of these types (INFP and ENFP) can be very whimsical, profound, empathetic, comical, sincere and more. However, the divide between introversion and extroversion causes a few differences in how they direct their processes in their way of being, rather than simply determining which type likes to be alone the most. There are outgoing INFPs who do very well challenging, encouraging and entertaining crowds and can maintain a wide circle of connections, which would make them seem extroverted. Likewise, there are highly selective ENFPs who choose to stick to a smaller group of close friends and don’t feel very comfortable around most people (although, from afar, they may still accept and love others as human beings), which would make them seem more introverted. The ENFP type (along with the ENTP) is found to be one of the most introverted among the extroverted types, possibly in great part because of how much their dominant Extroverted Intuition (Ne) picks up and gives them to digest, creating extremely unique perspectives, so they may have periods in which they could be confused with INFPs.
You’d have a seemingly ENFP who’s actually more of an INFP (whose primary four functions are Fi Ne Si Te) challenging, encouraging and entertaining a group, attending to numerous family and friends social events and keeping in touch. However, more than being invigorated by the endless possibilities and the amount of stimulation in these events, they are more drawn to them as a mission or a journey that they have recognized of moral obligation for the well-being of everyone and/or of deep significance to themselves (Fi), and proceed to weave everything together in clever, creative and humorous ways that can come spontaneously (Ne) and helps them loosen up and light others up, which may in itself become worthwhile and memorable experiences (Si).
And you’d have a seemingly INFP who’s actually more of an ENFP (whose primary four functions are Ne Fi Te Si) keeping to themselves, spending more time in solitary creative and research activities than actively and directly connecting with others. They may be hungry for ideas, leaping from one to the next and then back, seeing how it all connects and how they make or lack sense, constantly growing their web of interlaced points (Ne), yet, at the same time, this all goes to their internal value system of what’s right and wrong, what the world needs for the well-being of everyone and the actualization of what we’re meant for (Fi) so that they feel strongly about what they’re putting together and seek to help bring about big changes (Te).
So in telling these two apart we have to pay attention to where their actions come from and where they’re headed to, as both of them can have periods of appearing more like the other.
Some behaviors that can be found more often in one type than the other would be:
INFPs are more likely to have a wanderer’s air about them. (“I enjoyed the way the sand gently slipped through my toes and around my feet as I made aimless steps along the shore. The sight of the horizon was a comforting promise, and the sound of the waves reminded me I was not alone. I was wrapped in a warm breeze and I did not mind the saltiness in the air nor that the sun would soon hide behind the rocks…”)
ENFPs are more likely to have an adventurer’s air about them. (“I loved it. It was disastrous but it was real and true. I did not know what to expect, and it could be anything, yet I couldn’t wait for what was next. What would be of me, I couldn’t tell, and needed not to…”)
INFPs are more likely to be the fairytale characters who stroll around town inside a bubble, radiating their own inner worlds to the one around them. (“Untold stories within me are full of life…~”)
ENFPs are more likely to be the fairytale characters who skip around town, swiftly paint-brushing it with vibrant colours and throwing magical seeds into the air that effortlessly roll onto fertile grounds and instantly bloom. (“We must live and give life~!”)
INFPs are more likely to find it hard to contain from escaping to another world for their self-expression, and drift away. (“I’m searching for a secret garden, where sun-rays warm without burning and raindrops moisture without drowning. A place where the earth is both firm and flexible and the walls shelter without entrapping…”)
ENFPs are more likely to find it hard to contain from rocking the boat in their self-expression. (“I’ll be the flower that blooms through the cracks in the concrete if I have to be! Damn that effing concrete, though!”)
INFPs are more likely to be supportive through easing people’s conscience and showing them they matter. (“I didn’t think badly of it. Actually, without it we’d be much less. I’m glad it’s there.”)
ENFPs are more likely to be supportive through highlighting people’s potential and encouraging them to be grand. (“This is so amazing; I cannot wait to see how much more can come out of it!”)
INFPs are more likely to give off a soothing and nourishing vibe.
ENFPs are more likely to give off a reassuring and invigorating vibe.
INFPs are more likely to come across as endearing without even trying. (“I’m not cute! >///< You’re cute!”)
ENFPs are more likely to come across as enchanting by simply being. (“Oh, my spell is working then?”)
INFPs are more likely to show an innocent and/or childlike kind of humour. (“Why did the lettuce blush? Because it saw the salad dressing!”)
ENFPs are more likely to show a provoking and/or startling kind of humour. (“What is the recipe for Honeymoon Salad? Lettuce alone without dressing. ;)”)
INFPs are more likely to be accused of being ‘slow’, when they’re actually being extremely considerate of the human (and even spiritual) implications of the matter. (“¬_¬; How rude.”)
ENFPs are more likely to be accused of being ‘ditzy’, when they’re actually being brilliantly light-hearted and keeping others from burdening themselves too much. (“It’s so frustrating yet funny at the same time!”)
INFPs are more likely to accumulate feelings and express them once they’ve reached conclusions about them. (“I am done with this! I can’t believe people are being this way when clearly there’s so much more to it!”)
ENFPs are more likely to express feelings as they happen and let them amount to what they mean. (“But what are we doing with ourselves?! How can this be? We can’t keep doing this! We should do better!”)
INFPs are more likely to snicker at something they inappropriately find funny. (“Heehee X;”)
ENFPs are more likely to burst out laughing. (“Hahah, oh, whoops!”)
And so on…
(I hope this helped)
(Again, If anyone else also wants to add anything to this, I’ll appreciate it!)