What do you consider as a better all around plane a KI84 or a P38J?
Ki84 hands down, unless it's a mission to take to a seal clubbing, then the P38 has more kill potential. Only thing the 38 has on the Ki84 is ammo load imo.
From all my past experience with the Ki84, I honestly think it should be Eny'd between 10-15. Maybe 12 or so. I don't understand how it went up from 15 to 20. The only thing more mind boggling than that is the Mossie going from 25 to 30.
F6f might be able to beat it in rolling scissors but it is also significantly slower of an aircraft. Not sure about the F4u/Ki matchup but I think the Ki84 could eventually gain E edges on a D and 1a models but might struggle with the u4. F4U's are tough to beat slow against competent F4U drivers in any plane. The other planes you mentioned that can climb with it and chase it down can't turn with it except the Spit16. The spit16 is the ki84's only true nemesis in my opinion. Obviously the Spit9 and Spit8s as well but I think it is faster than those two and can run if need be.