Yeah no, I don't think
Fëanor is ENFJ. That's the type I think
Maedhros has. Diplomatic, thinks carefully before making a decision, has accurate intuitions about the feelings of others-- that is definitely not Fëanor lol!
I say Fëanor is ENTP because he's full of creative ideas, and is guided by his own internal sense of logic rather than logical
principles of others. I do think he
believes he's acting rationally, but it's his own
internal Fëanor Logic™️ that he's following. Whereas an ENTJ would place a lot of value on things like laws, which are
external principles of logic. I think
Manwë is a good example of an ENTJ.
Fëanor could possibly be ENFP, on the other hand. That would mean he's guided by internal feelings rather than internal logic. I could see that as well. But like I said, I think his own internal logic makes perfect sense to him and he thinks he's being logical. He's emotional, yes, but the classification of F or T depends on your decision making process, and I do think Fëanor makes decisions based on his own messed-up logic.