Paintbrush,
Ok, the Ki-84. It is a great fighter in AH, one of the best. It is one of the two fighters that I fly.
The thing about the Ki-84, and why I didn't mention it in the fighters I listed, is that to get the most out of it you need to turn off even more of the assistance. The Ki-84 is like an advanvced Spitfire in that it has more potential, but it takes more work to get that potential out. If you can get some of that potential out of it though, it is the premier brawler in AH.
If you want to learn the Ki-84 you'll need to learn to fly without combat trim. Combat trim tries to keep an aircraft trimmed for level flight at whatever speed the aircraft is going and in the Ki-84 that means that it trims heavily nose down as the speed increases. Once trimmed like that the Ki-84's already mediocre high speed elevator authority becomes worse, so bad that you can't even pull a blackout at 350mph. And that is a bad thing. With Combat Trim off and trim tabs all centered I can pull a blackout well past 400mph in it, and if I trim for nose up I can do even better than that. That one thing pretty much fixes the Ki-84's elevator authority in the speed range it should be fighting in.
Another thing to get used to are the combat flaps. They aren't quite the same as US combat flaps in that they don't deploy at 250mph, but once you get down to 168mph and get them out only a A6M, Hurri or Spitfire will out turn you, and none of those come close to matching the Ki-84's engine power. If you go into a tight spiraling climb almost nothing can get a shot on you.
The Ki-84's WEP is also special. US, RAF, VVS, other Japanese and early German fighters have 5 minutes of WEP and a 10 minute cooldown before it is fresh again. Other German fighters have 10 minutes of WEP. The Ki-84 has 1 minute 30 seconds of WEP, but only a 45 second cooldown. This allows the Ki-84 to burn WEP a lot more aggressively than any other fighter can afford.
If you like, let me know when you are available and I'll join you in the TA and practice some with you. Others that know a lot about the Ki-84 that I know can sometimes be found in the TA are Widewing and, I think, Wilbus.