I know INFP 9s, INFP 4s and INFP 5s. Oh, and lots of INFPs have the 4-5-9 tritype, the most withdrawn of the tritypes, as each of those Enneagram types is withdrawn.
The INFP 4 would appear to be the most common type of INFP (about 1/3, by some statistics I'm not going to bother referencing here). This INFP is very romantically inclined, but is remarkably skittish and shy, not bothering to maintain contact with people and even actually pushing them away (in a passive-aggressive way). They have their ideal of the perfect partner and even when they find someone who is close to that ideal, can't find the courage to take things to the next level. This is the type most likely to become a cat lady or crazy aunt.
The INFP 5 is rather interesting, as this is an extremely intellectual INFP, and can easily be mistaken for an INTP. The difference, especially when young, is that real INTP 5s don't give a shit about anything other than their particular specialty(ies). An INFP 5, instead, has very particular feelings, very particular tastes, and is quite adamant about it, up to a point. The INFP 5 I best know (a PhD computer scientist who models car engines for a living) is a dance partner of mine. One dislike of hers is that she refuses to pay for parking, and when she was driving us to a dance, she would park blocks away to park for free. But, here's the thing, INFPs respect others' preferences: if I was driving us, she wouldn't object to MY payinig $5 to park next to the club. Similarly, we were practicing one time and I put on a song and she said, "I hate songs like that, that take pop songs and turn them into salsa." I looked at her sadly, and then she said, "But I know this song means a lot to you, so let's dance it." INTPs don't reason that way.
INFP 9s and 5s are about equally common at 13% of INFPs.
The INFP 9s are perhaps the most social of these three types, as type 9s, while withdrawn, are the "go with the flow" and "go along to get along" types. INFP 9s, while very emotionally focused, are much more aware of the emotions of people around them than the INFP 4s and 5s. The 9s see all of the cross-talk, all of the needless conflict, and feel driven to fix it, often very passive-aggressively. (They're 9s, after all.) This kind of INFP, by virtue of being aware of others, is more drawn to be involved with them, if not very outspoken. (At least until the anger arises!) They have the same emotional nitpickiness that other INFPs have, but due to their more extensive interactions with people, it's a bit more obvious than with the other two INFPs.
