I only have the info here to go on, and a quick flip through some film clips. My impression of Eric Wen's video is that he misses the mark. Cillian comes across to me as pretty introverted - he seems to bring the world inside himself rather than going out into it. Quite a few situations where Wen claimed Se seemed more like a reaction to it, an interpretation of it, rather than the raw function. I spent my life being one thing at work and another at home, and Cillian seemed to be doing the same, though as a great actor, with far better skill maybe LOL. Wen also missed a couple of examples of Fi, I thought.
So ... Ni? Definitely - I think the way he described being immersed in a situation is very Ni. What may be unusual is that as an actor he is able to context-shift, and so he builds a new world for each role or situation. Many Ni dominant folks don't, or can't, do that, but this will go with being an actor who can successfully carry off a diversity of acting roles. He doesn't come across to me as a dominant thinker - he is forceful in his rational judgements, but they seem to be servant to his vision.
Something that tells against INTJ is that he lacks the arrogance. It's not that he conceals it when on interview, but that there seems to be none there in the subtext of how he talks and in his body language either - he actually came over to me as a humble guy, and that's very not typical INTJ. I felt there was quite a bit of Fe in his concern for creating a good show, and his reaction to going into the cutting room - it was interpreted as Te by Wen, but it could just as easily be to do with his social values and concern for others.
So here I am, with very little evidence, creating castles in the sky because I haven't really watched many of the things he's acted in
. So where have I got to - definitely I, definitely J, definitely N. I really can't decide between F and T. If I had to choose I'd go F.
(I haven't seen the videos you just posted yet Asa)