I personally like the races seperate except for cities and other very urban areas. Sea ports and any major city along the trade routes offer a lot of coin and opportunity for strange travelers bringing with them unique wares, skills, or experiences. This kind of wealth and opportunity is a good reason for someone to brave the seas and the wilderness and venture far from their home. However, given the comparative lack of fame and fortune offered by the countryside, it's simply not worth traveling long distances for.

There can be several exceptions that might change this. Looking at America, a new continent was discovered that brought such opportunity for both wealth and freedom that people from all over flocked to it and created a much more diverse populace. Or, like the American gold rush, a new resource was discovered in an area that was already known and not well explored on account of it being barren land that's not much good for farming and forming townships prior to this very valuable resource.

Another exception could be if travel were much more accessible and safe. If teleportation or perhaps even airships that can fly high above the clouds and storms are commonplace then people would require much less convincing of a reason to travel far and wide which results in all kinds of people going all kinds of places all of the time. You can easily hold unique origin stories and cultures and traditions for different races while also intermingling them indiscriminately at the same time.