Sovyrian vs Kyonin - How Are Our Elves Different?

So ever since I came across Pathfinder and dug into Golarion’s history and cultures, a question has haunted me: how are the Elves of Sovyrian on the planet Castrovel different from the Elves who inhabit the nation of Kyonin on Golarion? Despite two thousand years of divergence, they share a common source and, given Elve’s long lifespans, may not have grown so far apart. Yet even with a shared heritage, two thousands years weighs on Elves outlook and priorities. With so much time and millions of miles apart on different worlds, I cannot help but wonder that somehow these two branches of Elvendom must have somehow grown distinct, possibly only in small things, possibly only in priorities, or maybe in things of greater consequence that could set these two kingdoms at odds.
Curiously, I have come across nobody else, so far, who seems intrigued by this possibility. I’ve inquired in a few groups and boards, and the only response I’ve gotten is: Elves are Elves. No one seems interested in exploring difference or divergence between these two great Elven nations and willingly treat them as they same. And yet, if that is the case, and both Sovyrian on Castrovel and Kyonin on Golarion are so tightly bound, how then are they benefiting from this alliance? What level of exchange through the Sovyrian Worldgate keeps them aligned? What resources do they exchange and share? What support does Kyonin receive from its continent-ruling sister nation on Castrovel, which furthers its reconquest of the Elven homeland on Golarion, and drive out the demons corrupting its southern marches?
Either way, the rivalries between Kyonin and Sovyrian lie in their shared heritage, which deserves some treatment. Before -5291AR (4517 in Lashunta Chronology), the Elven presence on Castrovel was uncertain. The Lashunta tell legends of encounters with Elves - mainly as magicians or tricksters - from this early period. Yet verification is impossible. It is possible Elves had already established settlements on the continent of Sovyrian, and their visits to Lashunta-held Asana might have been sporadic. That all changed, however, when the starstone struck Golarion, destroyed Azlant, and sent the Elves retreating to Castrovel. Thenceforth, Sovyrian, and El its capital, became the heart of Elven civilization. This continued for 7,900 Golarion years (15,800 Castrovel), when the Winter Council and its allies responded to Treerazer’s threat ravaging Kyonin and chose to return.
Prior to the return to Kyonin, Elven influence had stretched beyond Sovyrian, through a connection of aiudara - elfgates - and colonies, including Qabarat, Ofu Laubu, Jabask, Candares, and other places. Elves and Lashunta together colonized Marastra - the continent now called the Colonies, and fought a long, bloody, and tragic war to resist the Formian onslaught. Though factions like the Winter Council never forgot of their heritage back on Golarion, most Elves on Castrovel were dedicated to building homes, communities, and nations. Elves were active on Asana, establishing a gateway hub at Qabarat, and subsidiary settlements all over the continent.
That all changed when the Winter Council sent forth the call and convinced many Elves to return to Golarion. When the call came to return to Kyonin, the Elves who went were highly motivated to reclaim their heritage, or also interested in claiming the opportunities beckoning from a new, unclaimed world. Conversely, the Elves who stayed wished to stay and retain their livelihoods on Castrovel. Unfortunately, the migration from Castrovel diminished so many populations that many Elven communities collapsed. Gate-settlements like Ofu Laubu, Jabask, and Candares became Lashunta, and only Qabarat retained an Elven population.
So what does this mean for the Elves who stayed on Castrovel? Since they chose to remain, I see them as being conservative in outlook. Elves had almost eight thousand years to become entrenched and wished to hold onto what they had wrought. Despite that, the lost population caused an inward collapse. Maybe not all the Elves who had dwelt in Ofu Laubu Jabask, and Candares wished to go to Golarion. Yet with the collapse of these communities, these remainders had little choice but to intermix with the burgeoning Lashunta or emigrate back to Sovyrian.
Population loss typically coincides with economic downfall. After the Withdrawal to Golarion, the Sovyrian’s Elves likely had to contend with subsisting in poorer fashion than beforehand. Fewer resources meant uncertainty for everyone, both common and noble. The great Noble Houses of El, despite fervent wish to cling to their heritage, likely had to make do with simpler means. In such benighted times, it is easy to envision an embittered elite no longer capable of maintaining their erstwile lifestyles, resentful of those who had gone to Kyonin, and now needing to share control of the aiudara-network with Lashunta, who though they had willingly allied with the Elves, all too quickly supplanted their former teachers in goals and prestige. I can easily imagine the Elves, who since Qabarat’s founding had influenced the Lashunta in science, culture, language, and philosophy, feeling pushed aside by their shorter lived, more vigorous, but arguable allies.
And yet Sovyrian and Kyonin still need each other. After all, who can understand an Elf better than another Elf? From Sovyrian’s perspective, all those resources and knowledge they had lost still existed a mere step and a gatefare away. For Kyonin, whose neighbors on Golarion are either mercurial Humans or Dwarves, they can rely only on their sister nation on Castrovel. While both kingdoms fear losing population to the other, and so restrict travel through the Sovyrian Gate, trade in information and portable resources - both information and magic - continues strong.
So support and competition between Sovyrian and Kyonin balances on a knife’s edge. they gaze on two different worlds and seek to address the challenge both present. Yet without each other, they have no one else. They either face their problems together or alone.