I really don't care about the inability of a rank newbie to use the Fw190A-5 as well as the simple roll on side and pull stick back into belly evasion of the Spitfire V. If you want to make that argument then the A6M2 should have a lower ENY than the Fw190D-9. It is much more appropriate to base the ENY values on actual aircraft capabilities and usage and how easy they are for a newbie to survive in.
As to the Ki-84 vs Spitfire Mk VIII, well, the Spitfire climbs much better, turns better without the finicky flaps, has better firepower, has 5 minutes of WEP and is faster at many altitudes. The Ki-84 turns better with flaps, has more fuel endurance, is tougher, rolls better, carries more ordnance and has fast recharging WEP. In a single fight the Spitfire VIII is probably superior, at least on paper, but the Ki-84 is probably the better warplane overall.