StCrispin,
Don't be afraid to come on here and ask – the 18th Century members are generally as gentlemanly as the period and are invariably helpful.
1) As the OFM says, most Continental units – with a few exceptions – had no buttonhole lace on their cuffs and lapels. The most notable exceptions were the NC, SC and GA regiments after the 1779 Regulations, although there were also one or two odd units from various locations before that, so you COULD use the Perry plastic British for them.
However, the poverty of those three States meant that it was unlikely this was widely observed (even the richer States up north had to make do with what they could get post-79, such as brown or dyed ex-British coats) so hunting shirts and civvies were probably the norm for them. Your figures, your call. Bear in mind, that many Continental units had more than one official uniform at a given time, and most changed their coat/facing colour combinations from year-to-year at least up to 1779, and in most cases thereafer as well. The late issue of clothing in many years often meant that the bulk of a unit fought its battles in their own clothes, with maybe only the NCOs and officers wearing any "official" uniform.
Now, most Loyalist units also seem to have done without buttonhole lace, especially after the move from green to red coats. There were several occasions when British regulars took their lace off, too – principally when they undertook "field modifications" to old uniforms when their new ones didn't arrive (eg the Burgoyne uniforms).
2) British uniforms changed a lot during the war
. and then again they didn't (ok, I may have lied earlier about us being invariably helpful
). The 1768 Warrant uniform was worn for the first year, maybe two, of the war, but popped up again in the South when some regiments arrived from Europe in 1781. Both Burgoyne's and Howe's armies modified their uniforms in 1777 – not in exactly the same ways, but often based on the fatigue clothing they had made from worn-out uniforms during the pre-war period.
The reason for the selection of hats in the Perry plastic box (and there'll be a similar selection for the Continentals and another for the Militia – all of which can be used by the British figures too, and vice versa) is that it gives you the chance to produce figures specific to one campaign or theatre.
3) You say you're a long-time fan of the period, what do you have in the way of books? Here is a list that would allow you to look up what information exists on most units in either army. Are you working to a budget (don't worry, we've all been there at some time)? If so, look at obtaining these titles via the inter-loan service of your public library:-
a) Uniforms of the American Revolution by Mollo & McGregor;
b) Uniforms of the Continental Army, by Philip Katcher;
c) Vol 3 of the History of the Uniforms of the British Army by CCP Lawson;
d) the two-volume Osprey Men-At-Arms titles on the Continental Army by Marko Zlatich; and
e) the two books on the American and British troops of the AWI (unusually, the Loyalists and Rebels are in the same volume), by Alan Kemp, published by Almark in the 1970s.
By cross-referencing these, you can usually have a good stab at painting up most regiments for some point in the war. And as I said earlier, if you're unsure about anything, you can always come back here. Be aware though, that there will be quite a lot of American units for whom we either simlpy don't know what they wore full stop, or more often we don't know what they wore at a given time; and then again, at other times, we might know quite a lot because someone wrote down what he wore at, say, Brandywine. If all else fails, units with a mix of hunting shirts and civilian clothing will cover most units up to 1779.
Hope that helped.