Turn off combat trim and it doesn't get heavy until well after 400mph.
That said, it is still better balanced than the Yak-3 as the Ki-84 is capable of participating in all aspects of the game, being in many respects a Japanese P-51D. Long range, good performance, good speed, bombs and decent guns. As an all round package the Yak-3 just can't compete, though it is a very nice duelist's fighter.
Karnak, one thing thats interesting is I can fly the hell out of a P38J, not Lightning in a bottle good, but I can hold my own thanks to guys like Baloo. I couldn't fly a Mossy for anything, one thing is its great for perk building, however I just can't survive in it.
I don't believe a Mossy should be 30 eny, maybe 20 or lower because of those damn lasers on the front (but thats just me).
Reason I say it, with the cockpit view I can fly like a tie fighter and in a reverse merge I can saw a wing off no problem, simply its easy to get kills in a mossy, its just hard to live in one.
Compared to the P40N? I'd be a mossy driver or at least attempt to fly one.