Welcome to the game
A trainer will probably get back to you soon, but I think for the most part they specialise in certain planes, rather than certain areas.
Also, from what I've heard (and yes, this may be slightly biased, but everything I know indicates it's true
):
-Warbirds sucks (poor flight models)
-WWIIOL is good if you want an all-rounder game, that models infantry combat too, but if you want a flight simulator then it's fairly poor.
-Aces High has the best flight modelling there is (which is almost certainly true, from my own experience), and very fun vehicle combat (+ excellent integration between the two, IMO), but it lacks infantry.
Anyway, hope you decide to stay here!