Ok, developing my 5e setting further. I could use some practical advice and help.

Map so far is here: https://dl.dropboxusercontent.com/u/803826/Gedwil2.png
(Everything north of Lorsa river is Rianneth, composed of kingdoms and others, most of the south is Clans of Mazerbaim, the Farassani peoples (sorta, it's a hodgepodge of refugees from across the southern ocean in Farsvia where most humans who don't flee have been exterminated by dragonborn)

(Among other things, I'd like to know if those subdivisions of the Kingdom of Gedwil make sense for fiefdoms. Scale is 1 hex = 2.5 miles; green is light forest/seasonal climate, yellow is grassland/more maritime climate)

Length background information and history follows.
Major races are human, centaur, otterfolk, dragonborn. Half-breeds are frequent, though only last a generation before their unnatural lineage is overwhelmed by humanity (half-faerie = elf, dwarf, gnome, halfling; half-fiend = tiefling)

'Lasha' are roughly western Europeans, Geddish = English, Lashances = French, Screyan = Slavic.

Chapter 4: The Borderland
The campaign focus is the Kingdom of Gedwil, which stands as a rear guard between the free peoples of Rianneth and the Clan hordes. To the west is Essenlí Bay, and vital trade to allies, and to the east the Deadmoon Mountains, home of countless demon-thronged ruins.

Geography and Climate
The Kingdom of Gedwil is bordered to the north by the Chesen River, and to the south by the Lorsa River. Both rivers run from the Deadmoon mountains, to the east, into the Essenlí Bay.
The northwestern regions of Gedwil are dominated by light forest, though large swathes of this forest have been cultivated over centuries into rich farmland. This area has distinct seasons. The bay can both soften the blunt of seasonal extremes and provide lake effect (essentially) snow.
To the east the climate becomes rather more arid, and Gedwil is dominated by a cool maritime climate.
The Lorsa River has one large bridge across it. While the Clans and Gedwil are enemies, treaties and careful negotiations still permit trade. The bridge is heavily fortified on both sides, and the bridge has been rebuilt several times due to warfare, even long before the Clans were an issue.
The Lorsa River is the primary defense against the Clans, who are not particularly skilled with ships. They have slaves who are, however, so Gedwil has still needed to fortify its southern border.
To the south of Gedwil are two large, and rather new, clans – Qafren and Imiqa. Qafren is led by a family that emigrated from Farsvia only 60 years ago, while Imiqa is controlled by an offshoot of the dominant Mazerbaim clan.
Generally, Qafren are more interested in establishing a coherent, functional region, while Imiqa is more intent on glory and destruction of enemies. Which is not to say Qafren are good – they have survived centuries of warfare with dragons in Farsvia, and are utterly ruthless.
In the short term, this means Qafren is a stable, quiet neighbor, while Imiqa is eager to start trouble. In the long term, Qafren is more likely to be a significant threat.
Political History
<400 AJ
Early in Lasha history, Gedwil was home to a number of feuding Lashances warlords, before a political marriage with a southern Geddish kingdom tipped the balance. Soon, the Chesen-Lorsa region became dominated by Geddish culture and kingdoms.
~350 AJ
Around 400 years ago, Gedwil was a trade hub in Lasha culture, situated at a vital spot between northern and southern kingdoms.
300-200 AJ
With the rise of the Undying One and his Screyan empire wiping out the Dun Uidoc of the far north, initially Lasha kingdoms did well. However, soon his necromancers set their sights south. As this happened, Farsvian refugees spread into southern Paccitanita.
~100 AJ
As northern kingdoms began to fall and southern kingdoms were overwhelmed with desperate refugees, Gedwil became a vital center for mobilizing action.
80-60 AJ
With great effort, and the unexpected help of a Screyan artificer, the Iron Lord, the Lasha were able to destroy the forces of the Undying One and banish him… which set the stage for the Iron Lord to attempt his own empire.
There was considerable interest in spreading northward, to reclaim old lands and conquer new ones, and the Iron Lord was overcome. The north is embroiled in war as different groups try to secure power.
The establishing of Farassani kingdoms in the south is overlooked by many, seen as just another sign of the chaos in the south.
37 AJ
Jeremain is born
10 AJ
Jeremain, Riannedd, Timmoth, and Bishop Gelgasonne enact a mammoth plan to unify the northern Lasha kingdoms into the nation of Rianneth. Among other things, a planned religion of Chozianism attempts to quell sectarian violence and create a sense of national identity.
0 AJ
Jeremain mysteriously vanishes into the Eagle Gulf, is anointed a Chozian saint, and the Gulf is renamed the Gulf of Saint Jeremain.
80 YJ
The Triangle War along the Gulf of St. Jeremain cripples economies in central Rianneth, followed by a magical plague which kills many.
100 YJ
Farsvians take over most of the southern Mezerlay, evolving into a horse raiding empire.
~100-130 YJ
Rianneth attempts a holy War of Liberation in the south, attempting to break Farsvian control. Disagreements and lack of communication result in a devastating losses. As a result, the Farsvians take over even more of the Mezerlay.
155 YJ
Present day. The Clans of Mazerbaim are still sorting out their empire and incorporating new holdings. Gedwil, once a central nation, sits as a rear guard against a vast (though highly extended) empire.
Culture and Trade
Eastern Gedwil is renowned for its olive oil. The arid lands near the Deadmoon are one of the most ideal locations in Paccitania for growing olives, and as long as a thousand years ago olive trees were imported from northern Farsvia to the region.
The Lorsa River was originally L’Or de Sang, or Gold Blood. There is some dispute as to whether this was a reference to the once powerful olive oil economic empire in the region or perhaps to an actual gold dragon or dragonborn.
Another olive oil cultural relic is probably responsible for the kingdom’s name. Huile is Lashances for oil, and some think that ‘Gedwil’ may have been ‘Ged de Huile.’
In the current day, the olive oil from eastern Gedwil is still a prized commodity, and one reason certain groups of the Mazerbaimdi are willing to trade.
Imiqa produces olive oil, but shoddy oversight and careless brutalization of slaves weakens its market. That and politics has encouraged oil trade between Gedwil and Qafren.
Eastern Gedwil also has a rather prosperous mining region, in one of the quieter portions of the Deadmoon mountains. Iron and copper are both valued exports.
Western Gedwil has a variety of products, though its economy rests mostly on farmland.
One advantage Gedwil has, economically, over many kingdoms further north is that it’s farmland and cities are long-established. By contrast, the northernmost provinces of Rianneth rely more on logging and clearing natural resources.