most games have their own way to show framerate. Games that use the same engine may all use the same way to show frames. You'll have to check on a game by game basis.
As for benchmarking, if that's what you want to do, some games come with a timedemo, but I'm not sure which ones and if they come with that for Mac.
If you just want to see which settings are best for you, I'd suggest just messing around with it and playing as opposed to hoping for an automated solution. Especially with complex games like WoW, where frames depend on so many things (area, graphics settings, number of people, effects on screen, server lag, et cetera).