My understanding is that the "real world" correlations of Easterlings are:
Wainriders (of mid-Third Age) = Huns c.400 AD (destroyed or assimilated by late Third Age)
Balchoth = Bulgars c.900 AD
"Easterlings with axes" "bearded like half-dwarves" from "the Wide East" = Rus (Eastern Slavs) c.900 AD
Variags = Varangians c.900 AD. Sauronic Norsemen. Can be from Khand (Khazaria) or from the Wide East (Rus)
Men of Khand = Khazars c.900 AD
Viniths (hinted at in the name "Vinitharya") = Wends (Western Slavs) c.900
The ME-Baltic peoples = "a host of the allies of Sauron that had long threatened the borders of King Brand crossed the River Carnen" (LotR) = Lituanians, Curonians, Livonians, Latgallians, Semigallians, Selonians, Oeselians, Estonians.
Men of the Last Desert = Men of the Gobi Desert c.900AD: Tanguts, Uyghurs, and Khitans.
The other 900AD peoples of Eastern Europe and Asia would have corollaries too: Poles, Moravians, Croats, Serbs, Magyars, Cumans, and so forth. The nearest ones are hinted at in the LotR: "And embassies came from many lands and peoples, from the East and the South, and
from the borders of Mirkwood"
That the Men of the East (ME-Asians) bear high cultures is indicated by how Saruman chose to spend over a thousand years dwelling among the Easterlings. Given his lofty interests, it's hard to picture him dwelling in the tents of steppe tribes. He probably dwelled among the ME analogue of Persia - the source of "magic." (Magi)
The Blue Wizards were probably based in ME-China and ME-India. Both are hinted at by Tolkien: in a draft of The Hobbit, there are references to the "Chinese" and the "Hindu Kush" mountains. Also seen on Tolkien's sketch map of the world from Shaping of Middle-earth.
https://atolkienistperspective.files.wo ... olkien.gif
I suggest that whatever kind of bows these peoples had in 900AD, their ME analog would have, in a similar way that the material technology of the Rohirrim and Dale-men are clearly modeled on the 900 A.D.-era Mercians and Swedes (Dalecarlians).
For more, see:
https://sites.google.com/site/endorenya