I'd actually assume that Lookshy and the realm have pretty much opposite systems of economics.
The realm mostly exchanges food for military power. They hire and equip legions of thresholders (and people from more marginal areas of the blessed isle) into military forces via giving them food, or the products that are created by this giant industrial production glut, IE, the fact that the realm can afford to maintain massive city populations who's job is to make cool shit. Realm legions are probably incredibly multi-ethnic and supported by clouds of local auxiliary troops. They may also be somewhat non-professional, with a large number of guys who the realm conscripts from agricultural labour when it needs them, around a core of those parts of the realm's society that are socially obligated to do warfare.
That would mean the dragon blooded, and any kind of military caste that the Dragon Blooded decide exists. Probably the decedents of the mortal soldiers built up for the shogunate/that served the scarlet empress and various great houses in the early days etc.
The Scarlet Empire is basically a service empire. It's soldiers are rice and salt and trade winds in a very literal sense. It creates military power by attaching its own military elite (dragon blooded and realm soldier class professionals) to massive swarms of local conscripts/mercenaries who it recruits with currency. Realm legions are often temporary or administrative affairs, based around the personalities of commanders, with only a few having a long history.
Basically, Vermillion legion is the most legion of all legions under this perspective.
Meantime, Lookshy is a power that exchanges military power for food. They have an arsenal of first age weapons and a large cadre of dragon blooded, and they use this to provide military services to the rest of the three rivers confederacy in return for submission, tribute and a flow of trade to the city. Food flows out of the East, from fields made fertile by the pole of wood, down the great river, to Nexus and the Lookshy, which each take their cut of their profitability. In Nexus's case, that cut is in the form of turning base goods, wood, grain, minerals, whatever, into finished goods, both directly (it's got factories and artisans) and indirectly (it needs grain to feed its artisans). In Lookshy's case, it's probably a lot of gifts, a lot of tolls they impose on the river to pay for their protection, a lot of semi-direct tributary relations.
On another issue, what do people think about putting another continent far out to the West, probably ruled by lunars who tore it out of the wyld?