I'm currently using 3f in my Brown Bess (11 gauge). Best patterns are 80 grains, 1 1/4 oz shot, lubed fiber base wad and nicked overshot card. No improvement with 2f, and since I'm using 3f for prime, it lets me use one horn. In my many years with a 12 ga Navy Arms double, I coincidentally got the best results with the same powder and shot charge, though different wad and card sizes, of course.
I'd try both, because I know folks that swear by 2f in their 20s.