I concur with the other posts in the general theme of 'the vertical.'
What I've noticed with the 'turny birds' is that there is a tendency to take everything into the turn almost immediately. Stall fighting/vertical remains a big part of the match, since you are trading "e" for alt, which simply puts most of the "e" into the bank.
Also, in your defensive turn it strikes me that you didn't pull hard enough. You attempted rolling scissors, which is a great step for something like the 190, though the Ki-84 should be able to turn hard enough to force an overshoot of most birds, then roll.
E (energy) is the combination of speed (kinetic energy) and altutude (potential energy). You can't trade E for altitude but you can trade the speed component of E for altitude. It's hard to decipher from your post if that's what you meant or if you meant that some planes can use excess HP to gain an altitude (E) advantage. I suspect the latter since you were talking about stall fighting.
As to the Zeke vs Grumman fight the Zeke is generally the better performer in the context that most consider (speed, climb rate, turn rate). Less evident the Zeke's probably still better in acceleration (excess HP), I'm unsure of low speed stability (both flaps in and flaps out) while the Grumman hold the cards in high speed roll rate and dive rate along with durability as Ink's already mentioned. Gun packages are approximately equal with hitting power going to the Zeke and rate of fire going to the Grumman.
If you can't exploit the few advantages the Grumman has the fight isn't lost. You have to instead exploit the pilot. Winning a defensive barrel roll, rolling scissor or brakes on overshoot are a few tricks in the bag that immediately come to mind and if the Zeke's on your six and you can't shake him simply keeping your wings out of plane with his might buy you the time to consider other options or for him to make a mistake.
The point being if you aren't considering every aspect of performance and ACM you're never going to beat a plane that's statistically better than the one your in and never going to progress as a virtual pilot.