Same Old Jew, the Israeli Water Engineer, still learning and blogging.
"She has no extreme racial identity, she could be almost anything." A lot of people say this about mixing all populations, but that's not how genetics works, it's discrete, like mixing skittles together, not like mixing liquids. So Megan Markle is definitely 25% african or so and 75% european, every genetic ancestry test will show those results for her. Also, traits in mixed populations don't disappear, they just change frequency. So a population that is 50% swede, and 50% Nigerian will still have kids who are totally blonde and blue eyed, but since these are recessive traits, they will be much less frequent, popping up from time to time.
As mixing continues, the resulting population is more homogeneous and generic.
No, again you don't understand, the overall genetic variation doesn't change, except by selection or a bottleneck.
The phenotype tends to the average look.