the ©Players Handbook is the defacto starting point for characters and races of the Steel Realms. The Human of the Steel Realms correlate to the Human of DnD.
Primary Variants forgo the general racial options in favor of a new race template specific to that variant.
Regional Variants only add flavor, replacing a few of the starting character aspects. Player characters from these regions need not adopt the regional variant, but NPC characters from the region should be assumed to follow this pattern.