The Fw-190 was fast as the Corsair because it was a small aircraft, compared with the Corsair. It's wing was even smaller than of Spitfire, P-40 or Zero's, or the P-51, being of reasonably modern profile and thickness. The modest size was the key to a good/excellent performance of the Bf-109, Yak La fighters, MC.202/205.
We don't know how much the convoluted air streaming through the oil cooler of the BMW-801 added to the drag. The engine installation was of low drag, but significantly helped by the 801 having a diameter of only 50.5 in.
The R-2800 was certainly fully developed - two stage (available in early 1942) or turbo compressor, with inter-cooler, capability for water injection, even a cooling fan was successfully tested.
The XP-47J, 500+ mph was claimed (though it's a turbo):
link. The P&W and NACA were experimenting with fan cooled radial before Pearl Harbor was attacked.
Plus the Bf-109F-4, Gustavs prior the G-6 (even without Notleistung ), the P-51A.