I think to the outside world, I come across more as an ENTP. I can be quite exuberant and crazy.
I really don't understand how people come up with the notion that the INTJ is necessarily self-confident. As introverts, I would suspect they can be rather insecure. An Ni dominant is likely heavily involved with internal conceptions, which are sometimes more important than making them a reality, especially when one doesn't have the resources to do so.
But I ultimately crave my alone time and for my lifestyle to be predictable and controlled, which I guess could lead many Ni dominants to be reclusive and perceived as eccentric by others.