With easy interstellar and supereasy intercontinental travel, you'd probably just get one big genetic group covering a wider area, so to speak, rather than several distinct ones. At least on the planetwide level. But with situations like the M23 one, then you'd get a helluva lot of that stuff. And with the size of the ER-verse, there'd be almost every kinda human genetic combination possible, before you knida got away from homo sapiens.
I thought that the ER-verse was sort of like WH40K: Humanity colonized as many planets as it could, something bad happened(Chaos/the Altered), and the ensuing chaos isolated most planets, then after a few thousand years the government (The Imperium/UWM) came through, fought off the (Chaos/Altered) and reunited the planets, but at the cost of establishing an oppressive government.
Yeah, that nails it, I think (don't forget to off-handedly mention lost and never rediscovered colonies
). Also, it should be noted that early colonies were often governmental ventures (not pan-governmental or whatever passes for "unified planet reign") or maybe even those of specific organisations/corporations/etc.; thus, it is not that uncommon for there to be quite narrower genetic and cultural heritage on some colonies than otherwise (and then those colonies became "inner circle" ones, pumping out yet more colony ships, so that trend continued, in a fashion).
Thus, I think on some colonies there still are imported "nationalities" and religions of the Earth, while on others a more even genetic and cultural mix can be observed, giving rise to their own new and distinct cultural and genetic groups.