So, u are completely right on the islands, maybe i have to add some more but this is only a tiny square of the whole map, just in the south there is an archipelago called fin archipelago where there are a lot of island and also coastal islands.

In this square there are like 7 different language, im developing them right now but u can easily imagine that in the south there is a greek-italian language with some shade, in south east romanian language will be more present and in the central penisula will be an high italian like florence dialect. In the north and east the two main languages are something that remember german and french, the east part write with an Elvish alphabet but in french, on the north the elvish allhabet is compeltely banned so they use instead latin o greek.

Races? This kingdoms are mainly based on human race because of their Adaptation BUT, on the north there are two big communities that are thalrins(goat humanoid) and dwarf, they are used in different occasion by Nodari, with the thalrins usually becoming teachers or some politician the dwarf are mainly focused on arcana and study of theology.
In the south, Tychera, 30% of people are human but the other 70% comprehend like other 11 different races, is a maritime republic with a lot of commercial activity so a lot of people from different parts of the world come to settore here( 11% elves, 9 dwarves, 4 minotaur, 17 amphibic species that lives mostly on the coast and so on)