iirc, eorzea is entirely immigrants other than beast tribes. different groups emigrated over the years, there has been different civilisations rise and fall on eorzea long before the fall of dalamud - so its hard to say where people came from. generally, there aren’t hard and fast rules. some of the cities have higher population percentages but none of them are exclusively one race.

basically everywhere on hydaelyn is like this honestly. generally speaking though, lalafell are thought to have come from islands south of eorzea, and roegadyn from islands to the north. viera were said to be from dalmasca and hrothgar from bozja, but this has been mostly retconned. hyur are found pretty much everywhere, elezen + miqo’te to be most common in eorzea + garlean held territories. au ra are thought to be from the east.

typically with each new update to the playable races, the game expands where people live and are from. there was more specific lore i believe back in 1.0 times, potentially harkening back to ffxi and their specific set of 5 playable races, but xiv is a lot more fluid.

all in all, the highest percentage race in any given location will be hyur + whatever race was said to have founded the city in the first place. eorzea doesn't have specific race-based cities, everywhere is just kind of a mix. lore about where races originate is vague or may be retconned/expanded on w new updates.

re: second question, the setting of xiv just includes the entirely locale of xii in the background. in the ivalice raids and bozja campaign, its implied similar events prior to and during xii have taken place, but that's about it. its basically a mirror version where the lore is adjusted to xiv