Reflecting cultural differences between mountain tribes in equipment and tactics

[Icelander]

In fleshing out a large region including a sizable mountain range with considerable foothills, rivers running into a huge freshwater lake and some thousands of square miles of subpar acricultural land that is suitable for herding sheep on most of it and grazing cattle on some of it, I'm trying to introduce more than one monolithic culture.

The reference society is a TL1+2/TL2+1 (depending on how you look at it) Mesopotamian-esque society that never fell entirely, but which has lost the empire it used to rule and for the past three hundred years has had an imperfect grasp on this region.* The Empire and the nation-state which remains after the fall of the Empire are both named Unther and the people are the Untheri.

I aim to have two ethnic groups living outside traditional Untheri society which are essentially Untheri in origin, but with minor religious and cultural differences. We'll call them Rammanu (Amorite-ish) and Assurites (Assyrian-esque). Then there will be people that are closer to the peoples living to the west, albeit much less 'civilised' and with traditions of irregular mountain warfare instead of organised warfare by citizens of a city-state. We'll call them Threskeli and they are very much Thracian-inspired.

For my fourth group, I'll have a group of foreigners from a subjugated province of an empire to the east, who had a difference of opinion with their suzerain about the degree to which they were subjugated and were granted asylum in these mountains, in exchange for service as soldiers and border patrols. We'll call them Zouaoua or Zouavas and they are Zenata Berber-like.

Now, while many of these people are peaceful shepherds and fishermen, those aren't the ones my PCs will need to deal with. I'm looking for distinguishing equipment, fighting style, tactics, dress and anything else which will be obvious when fighting beside or against them. Ideally, I'd want each ethnic to have something to identify them, at least to knowledgable observers.

Since the TL they have to work with is TL2-3, it is pretty much a given that all parties will use thrown rocks, slings and javelins fairly extensively. Those who have access to good wood may use bows, at least for the elites. Armour will be confined to the 'noble' elite around the warlords and their retinues. It's likely to be leather, quilt or something similarly low-cost, except for very successful raiders (who'll wear whatever they seized from the expensively attired warriors they defeated).

I imagine that the Rammanu and Assurites will wear kilts and sandals and be fairly likely to sport beards. They will be the most likely to be partially or wholly settled, and thus have more resources and be more likely to wear armour, in particular helmets.

The Rammanu, closest to the reference society and least likely to be subjected to virulent prejudice from them, might even have village levies who fight as shock infantry to supplement the light infantry most common to all factions.

The Thracian-esque Threskeli will favour tunics, caps, cloaks and boots, in contrast.

Only the 'barbaric' Zouaoua-like people will wear trousers, wide and baggy ones, at that, in addition to loose caps.

The climate is such that all three styles work and adopting or retaining one is a matter of demonstrating a cultural allegiance.

What about weapons and shields?

1) Does it make sense for the Rammanu to be 'known' to be the best slingers and in fact have a much higher proportion of people who can use them effectively? Or would that provide such an advantage over javelins that the other factions would have to adopt them or perish?

2) Could some of these tribes use round leather shields, some crescent-shaped wicker-and-hide ones and others round wood-and-leather? Or are some of these so inferior to others that it makes no sense that people fighting against them for generations wouldn't adopt them?

3) What about grip? Can some favour a buckler grip and others a fastened-shield? What would be the effects of that on their other prefered equipment and their tactics?

4) What are likely weapons for the melee, both primary and sidearms?

*The mountains and the western bank of the lake have pretty much always been outside effective political control of Unther (the Akkadian/Sumer/Mesopotamian empire), as it was more expensive to project power there than any reasonable polity could hope to gain from doing so.