I think it's more along the lines of how Robert Jordan described everyone. Nations had certain characteristics, but outliers were more common than if they were set "races."
Did we really see that? The Two Rivers is an exception, but other than places such as Altara, or along the border. the nations seemed pretty homogenous. It always seemed implausible - Did the previous sets of nations also have their own physical characteristics?
I'll have to try and look this up. I can't think of any Dark skinned Cairhienin, or Borderlanders. I think at least one of the Domani is decscribed as not looking like a typical Domani (ie coppery skin), but I couldn't find who it was. Perhaps unsurprisingly, we don't have a category/list in the library for "dark skinned people", "olive skinned people" or "pale skinned people"
Very true! There aren't really that many instances where race is that much of an issue unless it's directed toward Aiel-centric slurs. There are some sideways looks at the Tinker lifestyle, but the worst prejudice seems to be around people who can channel. In a world that doesn't have many technological advances, the fact that people who can channel exist will be the main source of anxiety. They're powerful and unpredictable in ways WoT Muggles aren't.
There are definitely expectations of the variously represented ethnicity/nationalities, though. You could potentially go so far as to call them stereotypes, but I'm not sure if "prejudice" would apply. The best example that springs to mind is the expectation of Domani women to be manipulative, sultry, and wearing what citizens of other nations would think of as revealing clothes.
Part of these things are to set up and establish worldbuilding and distinct cultures within Randland, but they simultaneously erect mental expectations or, again, stereotypes. I will be interested to see how the show handles the task of representing this multitude of disparate cultures.