I'm pretty sure function -strength- is set in stone, but preference to each person varies things. The 'Humanist Scholar' subtype probably goes Ni/Ti > Fe > Se (Well for me, Inferior Se is just a troublemaker 90% of the time. But it's nice when I need/want to connect with the SPs and SJs out there)
The 'Humanist Friend' subtype probably uses Ni/Fe > Ti > Se (Though from the above, there are exceptions)
Those are the main 2 subtypes of the INFJ. I haven't found any others yet (Though there could be the 'Humanist in Se Clothing' that uses Se primarily)
I've personally started wondering if I'm a strange love child of an INTJ & ENFJ at times.. Or an INFP.
I always felt 'Somewhere between ENFP and INTP' - My room is a total mess, so is my workstation in school. I guess that fits under the 'consistently messy' category in one of the profiles.
It could be a gender issue: since it was discussed here that female INFJs tend to rely more on Fe while male INFJs rely more on Ti.
Society drills it into us that Men shouldn't have Fe, so we hide it and express Ti more. We're also stuck waiting until the mid 20s to really start relationships cause all the young girls want the ExTPs
( There's an about the Dark Tower series by a band called Demons & Wizards, the album is called Crimson King - I was like 'OMG awesome' when I figured it out since I had the album for at least a year now. If you like Eurometal and the Dark Tower series, you'll love that album. It goes through the whole series: '1: Crimson King, 3: Terror Train, 5: The Gunslinger. Guys go to iTunes and download it. Its awesome!)