syracusepops,
The Badger & FoxtrotPapaRomeo have already given you some very good info and put up links to a useful previous TMP post on this topic and also to the page on my blog dedicated to the Afghan regular army, but as someone who's spent many years trying to learn all I can about this obscure oddball topic, sorry but I still have to add something!
As mentioned above, for the most part the different types of headgear should be used by different types of troops. For instance Turcoman (also known as Turkmen, Turkomen, etc.) units would wear distinctively Turcoman hats. At the time of the Second Afghan War, ony one Afghan infantry unit is generally known to have worn imitation foreign service helmets, the so-called "Highland Guard", probably the most famous Afgan army unit of the period, which is not known to have been present at any of the major battles of the war, though it is possible they were part of the Kabul garrison mutiny which led to the attack on the British residency in September 1879. I confess I often use them in battles were they probably weren't, simply because I think they look pretty cool. Most Afghan regular infantry of the period are generally described wearing the Afghan "beehive" hat or turban, and some units appear to have worn a mix of both.
When it comes to "elite" units of the Afghan regular army during the Second Afghan War, the only ones I know of that can be said to qualify were the artillery, who generally acquitted themselves well enough for some British journalists to claim the Afghan guns were commanded by Russian officers. In fact the guns were commanded and crewed almost exclusively by members of the Qizilibash minority community, who were descendents of the Persian invaders of Afghanistan and India who stayed behind -- mostly in big cities like Kabul and Herat -- after being part of Nadir Shah's invasion of Mughal India in 1738-1739.
In general, as also mentioned above, think of Afghan regulars as similar to Egyptian regulars -- basically second class versions of British or Indian troops. Probably their only real advantage over their tribal counterparts is the fact that they were all armed with some kind of rifle, or in the case of cavalry, carbine. During the 1878-1880 war, these were mostly Enfield rifle-muskets and locally made copies of the same, with a smaller number of units armed with Snider-Enfields and locally made copies of them as well.
I believe there is one recorded instance of an Afghan regular infantry unit forming square during the course of a fight, but I think it was a small action and not one of the 8 major battles of the war.
Finally, here's a nice contemporary illustration of some Afghan regular cavalry, with one carrying a typically triangular banner mounted on his back, in similar fashion to a Samurai…