One of the big questions you face when working on an interstellar science fiction setting is: Just how many people does a colony start with?
Cue this timely article by Popular Mechanic. They assume colonization by generation ship, but I think the results are still applicable if you simply look at the colony at its destination. It takes between 10000 and 40000 people to maintain genetic diversity and guard against accidents that wipe out a substantial number of colonists. As a side note, the authors also recommend that it’s better to send a small fleet of vessels rather than one big ship – but that sort of redundancy is pretty much a given if you are sending that big an expedition.
10-40k is a really good match for population characteristic value 4 (“tens of thousand”), and you could assume that any world that has Pop 4 and a TL that is close to your setting’s mainline technology level is a fresh young colony – especially if it’s out in the periphery.
At first glance it might seem that colonies are big busy places – forty thousand people is a fair-sized town – but keep in mind that this is the entire population of an entire planet. They’ll spread out at least a little bit, into homesteads, camps, and outposts, and the main settlement with the starport won’t be a very big settlement at all.
It’s also worth noting that 10,000 individuals is the assumed number of survivors during the Toba catastrophe human population bottleneck.