The four coastal cities of Candiels (1894gold), Paisly (1728gold), Golden Farrow (3086gold), and Eidulb (2159gold) have a population of 1 each so they would require a long time to recover. Candiels is too far south for any realm to make an attempt to retake besides Fissoa with D'Haran help.
Echiur and Darfix have the highest current populations but are on the far side of the continent and unreachable. Chateau Saffalore has a population of 1138 out of 16893 but would require securing the townsland of Saffalore (population 1) first and isn't a particularly wealthy city (943 gold) so it would have trouble supporting militia and other costs.
Excluding Echiur and Darfix, Libidizedd has the highest population with 4348 people (max pop. 37732) and would make a good capital for a colony to settle the west. It is reasonably wealthy (1905gold) as well. Across the cobalt gulf, you have the city of Eidulb and its townsland plus, the stronghold of Shrine of Seeklander directly to the north that would all have potential fortifications to help with resettling.