I was someone who loved Tilly last season. I dunno what is rubbing off wrong this season, since tonally it's a bit lighter and you'd think she'd fit in better. But at least in the first two episodes she's coming across much more as if she wandered onto the set off of another show - as if she's been awkwardly shoved into the plotlines with a crowbar.
200 years is on average considered around eight generations not four, however, children can be born to women in their 40s. The actress playing the priestess is in her 60s as an example. That would mean i the character is around the same age she was born 130+ years after the people arrived. So, realistically she could be as early as a third generation settler if her grandmother arrived as in infant or 7th-8th. What I was pointing out was that, dependent on the diversity of the genetics people transported (which we don't have an answer for in the episode) its likely the entire colony of people wouldn't necessary appear or even be homogenously biracial within 200 years of arrival.
The average generation length though is 29 years, throughout human history. Women can bear kids starting in their teen years, on average till about age 44, but the median has remained around there until quite recently.
I agree people wouldn't be homogeneous completely in terms of their looks. I mean, a real-life example is the Uighur in northwestern China. They're roughly a 50/50 mix of East Asian and West Eurasian (mix of "European" and South Asian) in terms of their ancestry, and have been thoroughly mixing for 1,000 years now. Mostly they're very mixed in terms of looks, but occasionally you get people like this popping up:
Despite those kids looking "white" genetically speaking they're probably just about the same percentage East Asian as the average Uighur (about half). It's just that they happened to get the genes for blond/red hair, light eyes, etc. Still, this is rare - and western journalists make it seem more common than it is because these sort of photos make us turn our heads.
Regardless, presuming the demographics of rural Indiana are still mostly similar by the 2050s in the Trekverse, I can buy New Eden having "white people" fairly easily. It's harder for me to swallow logically black men as dark as Jacob, because his ancestors would have to have been interbreeding within the black minority for those eight or so generations - which is very unlikely without some level of racism or segregation.