As I was playing modded Skyrim the other day I was remembering how at one time I thought how epic it would be if it was made into a movie. Definitely not not anymore. If made today, how do you think they would butcher it? Obviously the main character would be female and the Dunmer in Windhelm would be the focus of the story.
I still think it would be cool if a great fantasy author wrote a 12 book series about the history of Tamriel or a series on the adventures of past Dragonborns or Morrowind. So many possibilities
Almost always, yes, a Redguard mother and a Nord father would result in a Redguard child. The child obviously gets some traits from the father, which can include skin and hair, but the overall trend is towards the racial standard. There's a handful of exceptions, but they all predate the lore revamp in the Redguard/Battlespire/Morrowind era.
The Bretons are the clearest example of race essentialism in TES. The Ayleids almost certainly looked like Altmer (if they weren't just Altmer outright), and the Bretons were just tribals they took as slaves. They intermixed for generations, but all Breton are still short, still have round ears, and do not have yellow skin or sharp eyes.
To make a very long story very short, yes, the races you see in TES are all functionally distinct classes of life. It's unclear at what point the mannish precursor spirits became the races of men (and fundamentally unanswerable for reasons far too complex for a short answer), but they definitely do descend from distinct spiritual/mythic forces. If you dig deep enough, the Atmorans and Yokudans (Nords and Redguards) might literally be aliens not only to each other, but to Nirn as well.
I'm leaving a lot out here, but you get the picture.