I'm not afraid of Me-109s. In fact, they're my favorite foe—while different from the P-38, they seem to be exactly equal overall. Of course, the real reason they're my favorite opponent is because they were historically the most commonly faced enemy of the U.S.A.A.F.
Ki-84s, on the other hand, are a definite problem, about as much as a Spitfire Mark XVI (except for at very high altitude).