(Setting the unique origin of the Twilight People / Zath aside for a moment.)
The "two creators" made the physical, "bright" world, and all the other deities. They only made the Sun People directly, the rest of the "races" (meh I hate that term) were made by the other deities. They're all human in a general genetic sense, but they've been influenced by the deities that favored them. So the Moon People were influenced by the Moon deity, the Storm People were influenced by the Storm deity, etc, but most humans were influenced by the Earth deity... however they're rarely called Earth People because it was the default, and because of subsequent events.
When the "two creators" were destroyed, they shattered into countless motes of "divinity" which scattered about the world. Over time these lead to the rise of many smaller deities as motes coalesced around local beliefs and fears among the struggling humans. As faith in the "twin suns" was widespread and deeply encouraged among the servitor classes, a good deal of this energy was drawn to the direct child of the "two creators" who was a fledgling solar deity, and became the new Sun deity in his own right -- it's this Sun deity who the various "solar cults" worship now.
So at present in this setting there are the deities who were the direct children of the "two creators" (Sun, Moon, Earth/Soil, Storm, etc), and also the regional and local and family/ancestor deities who formed from the scattered motes, and the various spirits and totems and such. The line between "local god" and "powerful spirit" is very blurry -- a great river or mighty mountain revered locally as a spirit could easily have "drawn in" enough of the divine essence to become a deity.
Spoiler: And then there's the Underworld/Fire deity...
...who is via deception and guile and the strange impossible magic of the timeless Darkness... the daughter of the "two creators" AND the Darkness. None of the other deities know this. She holds fire in one hand and shadow in the other.
E: got cut off and had to hit save earlier, forgot to come back and finish this... now it's way past when I should be asleep, so short version.
The original Storm People were a single "ethnic" appearance as I described earlier, with ocher or terra-cotta or copper-hued skin, almond-shaped bright-colored eyes like the sky or the sea (blue, green, grey, hazel), and dark hair. Their culture was something of the "frontier edge" of the Solar Empire, but still an imposed order with them doing the hard work of fishing and building and such, under the direction of the Sun People.
After the Solar Empire fell with the mass death of its ruling caste, there was a lot of churn, and a lot of intermarriage with other human "ethnicities" around the edges, bringing in dark eyes and swarthier skin in one area, lighter hair colors in another area, etc, giving rise to much more local variation in appearance, and at the same time as things really fell apart there was a long period of isolation as the capacity to maintain or replace the large ships was lost (engineering and similar skills had been reserved for the Sun People, who were all dead, and the human elites, who largely killed each other off trying to fill the power vacuum) resulting in a lot of localized cultural drift and a lot of starting from scratch as specialized knowledge was isolated or lost.