Just going by the stats, the N1k2 is faster than the F6F below 10k, accelerates a hair faster, turns noticably tighter (more so with full flaps) and climbs significantly faster than the F6F. At speed F6F has an edge for sure, but the N1K2 is one of the few Japanese planes that doesn't fall apart at high speeds in this game, so if anybody can give the F6F a chase it'll be this plane.
I think in this setup the allies are going to be more effective with the F6F than with the FM2. FM2 might be manuverable, but it's also slow, underpowered, and under-armed. Being 50mph slower than the other planes means it can't get away, it can't chase, can't zoom as well, etc. I think the F6F will be the real killer for the allies (just thinking of past FSOs with Hellcat, it's quite effective)