Ken,
Good choice! Can't get better AWI figs, IMO.
Because of the size of typical BG battalions, and the "fire and charge" tactics adopted for most of the war, most people just mix all three poses across however many bases your unit has. Have a look at this excellent blog to see what a typical firing line looks like on the table:-
http://gilesallison.blogspot.com/2007/06/british-light-infantry-1.html
(I know it's a Light Infantry battalion, but the same principles apply; look out the 20th and 21st Foot on the same blog for line units.)
For the record, in theory the British still used the form of "platoon fire" proposed by all the manuals of the time, such as Bland. However, throughout the 18th Century accounts suggest that platoon fire in all armies went to hell in a handcart after the first one or two volleys. Also, after the New York campaign, the British pretty much settled on a single volley at close range followed up with a bayonet charge.