I've been thinking about this a lot lately. I think the ideal racial caste system would probably be pretty nuanced, but the general idea:
White people on top, obviously. White men above white women, white women above white trannies, all white people above all other races.
Next would be half-breeds, particularly ones recognized by their white father. Basically any kid born into a white man's harem. They aren't white and will probably need to be reminded of that once in a while, but they're still more important than their lessers. The males aren't necessarily allowed to breed, and ideally are feminized.
The general idea for any non-white community is that when the girls reach 18, they're inspected and it's determined whether they're fit for marriage/breeding. Ones that are receptive to marriage and obedient can enter a white man's harem, but ones that are rebellious/problematic become a public utility, possibly in state-sponsored minority/state enemy brothels. The men who aren't feminized, as well as the non-fuckable women, are allowed to live in ghettos/enclaves where they work jobs tailored to their race's talents. Kikes in money-oriented jobs, spics and niggers in labor, chinks and Indians in restaurants, etc.
But for fuckable women, the general idea is breeding by white men until their worthless genes have been replaced.