I fly the Ki-84 pretty regularly - frankly, I think it is one of the most under-rated and lethal rides you can take. In a Ki-84, I don't fear taking on anything - rides that are faster than me can't turn as well, and none of the uber-turners can match my speed. Good climb rate, and the cannon package is sufficient.
I've killed La7s, Spits, Nikis, F4Us, 190s, Ar234s, Bombers, etc. etc. etc. in the Ki, nothing is beyond the realm of possibility in this really nice ride, and anyone that takes you on in one has to worry about you suddenly turning the tables on him.
I haven't actually found the need to take drop tanks - the range is good on full fuel (especially if you throttle back a bit to cruise setting). Since I'm stuck with 250Kg bombs anyway, I'd rather keep 2 instead of trading for a drop tank.
EagleDNY
$.02