That's interesting that you've seen ISTP and ENTP Threes. How does Introverted Thinking figure into that style at all?
Ti, as far as I understand it, is supposed to figure out how something works. It's "subjective logic," as Lenore Thompson describes it, used to "coordinate our behavior logically with immediate sensory data."
From Personality Types: An Owners Manuel:
"INTPs see logical implications in terms of systematic change over time (...)"
"INTPs are likely to be more interested in the idea that animates a system and its impact on reality than they are with a system's objective utility."
Even more action-oriented ISTPs probably wouldn't have much concern for understanding something for the sake of making themselves look better, or at least, not in order to construct a consistent image of success.
If a Three used dominate Introverted Thinking, perhaps he or she would be a good trouble-shooter. Someone who quickly produces solutions to problems. In a professional environment this could bolster his reputation, but dominant Introverted Thinking naturally conflicts with the social adaptability of a Three. With Extraverted Feeling as the inferior function, "these types can be nearly oblivious to the social rituals and signs of relationship that Extraverted Feeling regulates.
3w4s may be more introspective than 3w2s, but as Threes, they are still primarily extraverts, right?
However, for ENTPs, things may be different:
"Unlike ETPs, who involve themselves in whatever turns up and may not know what really suits them, ITPs know exactly what they are good at, and they don't feel the need to do much else."
In the Heart Triad, Threes are the most removed from their feelings. They put them aside in order to complete tasks. Extraverted Judgement would make sense in relationship to that.
However, would inferior Introverted Feeling be responsible for driving ETJs to experience one of the basic fears of a Three, such as feeling loved for the image and the performance rather than the true self?
"Although ENTJs are not naturally tuned into other people's feelings, these individuals frequently have very strong sentimental streaks.
Often these sentiments are very powerful to the ENTJ, although they will likely hide it from general knowledge, believing the feelings to be a weakness."
(Personality Page, ENTJ)
Also, could we make a case for ESJs more often being 3w2s while ENJs are more often 3w4?
I feel like I am going in circles trying to find perfect correlations between the enneagram and functions in Myers-Briggs.