I was imagining the Transbalkans as a blend of Greeks, Albanians, Bulgarians, etc. who more-or-less survived WWIII by banding together. This habit continued even after First Contact, and they kept their identity even while welcoming all the benefits of a United Earth and later the Federation. Nevertheless a sizable number quite liked the idea of a world of their own, and this one--800 light years from Earth--seemed a good choice. They are not an isolationist or xenophobic group particularly, but they are rather private.
Some might find it upsetting, but in my mind they retain a version of the Orthodox faith, one as different as the Church is today from that five hundred years ago.
Omega Capricorni VI itself is on the dry side, with no moon hence no real tides. Native life, with the exception of some lichen and such, is entirely in the oceans. Colonists have centered their efforts around a lifeless inland sea, and are very slowly, very carefully increasing the oxygen in the atmosphere and developing versions of terrestrial biology compatible with what already exists here. Such a challenge has attracted some top-notch terraforming experts from all over the Federation, some of whom have stayed.
On another note, I've taken the liberty of creating an article for you, with links, on the Star Trek Expanded Universe wiki. I hope it puts more eyes/ears on your awesome works.
As well, I added links to the YouTube illustrated audio of Chronicle on the (already created) articles for Chronicle and USS Witch of Endor.
In my own Star Trek: Shadowstar Station universe, I've posited that many Southeast Asian peoples (I'm half Indonesian and half-Filipino) allied themselves and formed a few different colonies, both established by sublight vessels before 2063 and warp-driven vessels afterwards. I like your idea of a Transbalkan ethnic group. I suspect also that the different Scandinavian nation-states pooled their resources to go to space, though those countries would have less population pressure to inspire such an exodus.