Likewise
@Androthelm ^_^ can't wait to see what kind of story we'll end up writing :-)
I thought about the data that
@Tharmáras shared about the Swarthy Men and their eventual migration to Beleriand and here are some of my musings. Get a drink, get a snack, it's a long one...
They were short and broad, long and strong in the arm, and grew much hair on face and breast; their locks were dark as were their eyes, and their skins were sallow or swart. But they were not all of one kind, in looks or in temper, or in tongue.
When I first read this description I was immediately reminded of the
Morlachs and
Vlachs. Granted this is somewhat biased, because my MA thesis dealt with them, and honestly most of my academic writing was in one way or another connected to the population of the Croatian and Dalmatian military frontier in the early modern period. But, but look at the moustache on
the guy with the chickens and tell me that's not a Swarthy Man!
Although I couldn't find any information if the Swarthy Men were sedentary or nomadic people, I'm leaning more to nomadic. I'm thinking they move frequently, and they move their livestock and people in the pattern of
horizontal transhumance that is more susceptible to being disrupted by climatic, economic, or political change. Having that in mind, climatic change (let's say a volcano eruption, or sudden change in the wind pattern) triggered their migration from their homeland toward the West, and the afore mentioned factors (not only being promised rewards in the form of land by Morgoth's emissaries or the Elven emissaries) can be the main reason Bór's and Ulfang's tribes move. The promised rewards are just the final push, the swing vote.
Of course we don't have to go into complex tribal politics

or list reasons why historically tribes moved or even go into the whole transhumance thing... I'm a historian and I like these kind of things, and exploring tribal politics, culture and how climate affected everything would be fun for me, but I understand that's not the main focus (or even the point Nessa!)

of AoA.
Before I forget, for writing inspo I wanted to highlight how the Swarthy Men differ from the Edain not just in clothes, but in weapons. I was inspired by the
weapons of the uskoks, if you disregard the flintlock weapons and the schiavona, the rest seems something that these people could be using. Heck, while I'm at it and if you haven't already fallen asleep here are some clothes inspiration:
uskok uniform and
Alkar squiers