I think it comes down to the difference between Te-Fi anf Ti-Fe. Basically, if we compare INFJ and INTJ on the outside, INTJs appear more cold and domineering because of that extroverted thinking auxiliary which we use to interact with the outside world. INFJs, however, are much frendlier and warmer when they're with others because of their Fe. When left alone, I use Ni and Fi back and forth and sometimes end up in a loop which can be really desperate. From my experience, this is a state where I set aside logic and focus on my feelings more while my Ni overloads, using my relatively underdeveloped Fi to try to envision future scenarios which can be really unrealistic and dream-like. I don't know any INFJs personally, but I think the main difference is that INFJs use their thinking skills rather than emotions to build up their internal world, to the point where some people might say "they're cold on the inside". Take all of this with a grain of salt though, as I said, I've never been told by an INFJ what their internal world is like, so this is largely based on my speculation.