This is the MBTI version for your question, correct? I accidentally started posting this response in your enneagram thread.
I'll answer the question as an INFJ (although I've debated internally about my type, so here goes)
Other people seem like Ni-doms to me mostly when I sense they have a particularly rich inner world that is attempting to make sense of the whole of reality. People like Carl Sagan focus not just on the structure and nature of the universe, but when reading his writings you see he is constructing the meaning behind the whole of reality. Even controversial figures like David Icke exhaust their mental resources attempting to understand how every pattern converges into a meaningful whole. It doesn't necessarily have to be focused on the universe itself, but the Ni-dom's inner construct of reality is so developed that their external nature tends to be quiet, understated, even bland at times, but they truly live in a parallel universe inside their own minds. Sometimes a Ni-dom will have the fortitude to affect external reality by shaping it somewhat into their inner construct, but I think the primary aspect of Ni is its true nature as a perceiving function, so the majority of Ni-doms are content to ponder the outside world and construct their inner concept of it. It is possible for a Ni-dom to perceive reality with sharp accuracy, distilling it into a more condensed version of core associations into their inner construct. These Ni-doms have insight that is pointed and accurate about external reality. It is also possible for a Ni-dom to construct an inner reality far removed from the external nature of things and so be an individual prone to inaccuracy when dealing with reality. In most cases there are elements of both: moments of pointed insight, and moments of internal subjectivity.
When the Ni-dom also has strong Fe as in the INFJ, I've read so many descriptions that say this means they will tell you what to do, or be socially forceful, reducing Ni to tunnel vision that jumps to intuitive conclusions that must act on reality. I don't think that is the primary nature of it, although it can happen depending on environment, culture, and enneagram type (although the richness of the inner world will still be apparent, which is not in most socially forceful personalities that are entirely invested in the concrete outcomes of their actions and ideas). In most cases the Ni-Fe is a person strongly affected by the emotional climate of the external world, which can be internally amplified by the internal construct of patterns gleaned from the outside world. They analyze how people interact, how the inner systems of other people function, how their own system is part of the larger system of perceptions and people. They will come to conclusions about these external systems, what makes them healthy or unhealthy, the cause-and-effects interacting, but this doesn't necessarily translate into social action. It can, but the true nature of a Perceiver is to view and understand, to make sense of it the way it exists on its own, and then to translate that into the inner reality. Ni-Fe sees the subtext in human communication, it looks at patterns that lie beneath the surface and not the literal words spoken. It sees coherency or inconsistency between what is said, the subtext of what has been said, and the non-verbal cues. There is an awareness when these are authentically aligned or when they are in-congruent implying falseness. When understanding this, there is no tunnel vision, but what may be perceived as narrow focus from others is the small corridor between the inner and outer realities. There is no jumping to a quick conclusion because and ocean of analysis and interconnected observations are driving the conclusion on both a subconscious and conscious level.
There is some type of person that lives in the abstract, metaphorical, hypothetical, and imaginative aspect of reality. This isn't just having some type of inner vision one must impose on reality, some thought of the future, or even some intuitive leaps when analyzing information, which I think every human being possess, it is about an entire way of relating to the outside world that views it through a different lens.
