For discussions I think the most important thing is getting the massive variations in how people mobilized their armed forces right. Rome, Carthage, and over in the east China are massive outliers among state societies in just how efficiently they could turn population into military power. Imperator got the Diadochi mostly correct, but it also made their mobilization model standard for literally everyone in a way that doesn't map to actual history. The way non-state peoples like the gauls and germans could moblize populations above and beyond any state society, though of course without the same qualitative factor, is pretty important too. The floor of moblization rates begins at what Rome could theoretically manage (around 8%) and caps out at literally everyone. Imperator made a token effort to represent that with tribal migrations but it doesn't really work in practice, and the AI doesn't bother reenacting the Cimbrian War with it, partially because you actually can't due to the lack of causus bellis you can get as a migratory tribe.