THe area of what is now NW Greece and southern Albania at the time was known for using skirmish style troops, peltasts and such. Mountainous areas within the greater Greek world generally produce such a style of warfare, light javelineers, slingers, archers, for use in raids, see Thrace, Crete, etc. By the time of the Successors and the late Republic, I'd concur that the armies of Epirus would be much like the Successors, perhaps lighter on cavalry and phalanx and more skirmishers, but supplemented with Illyrians, Celts, and other troops from the greater Greek world.
As for the national symbol as Epirus was a monarchy, it would likely be the king or a royal symbol, like the fasces for Etruscans/Rome. Albania's symbol is the double headed eagle, but I would suspect that since ethnic Albanians are in fact Illyrians, the symbol is Illyrian in origin. Then again, I'm mostly Germanic with some Baltic and Slavic mixed in, so what would I know?