Colonies and Outposts

RogerBW

General Arrangement

The structure is tighter than the Commonwealth but looser than Empire. Colonies pay some taxes to the country that founded them, and are expected to trade primarily with it or its other colonies. Some of the older ones have become independent, amicably; it’s written into their constitutions that they may do so if enough of the population wants it and their economies are strong enough. (Some colonial powers are rather less liberal about defining “strong enough”.)
If a colonial resident wanted to move to and live in England, that would be no problem. If a few thousand all wanted to move at once, it might be a bit more sticky.
Life on a colony is slightly lower tech than on Earth, though it’s catching up, and you probably have to do an actual job, perhaps for as much as twenty hours a week. (How can they live like that?) Communication with other worlds is asynchronous (written, audio or video messages) rather than interactive, and the colonial sense of identity is fairly strong.
A colony is there because it’s a place that can support human life, and an initial group of at least 10,000 people could get together and afford (or get someone else to pay for) the shipping costs. Often that was a group with some strong sense of “us” about it, perhaps religious or ethnic; it may have drifted somewhat since its founding. Often there was something valuable there too which could be sold to pay back setup costs: rare minerals that could easily be extracted, odd biochemistry in the ecosystem leading to new drugs, etc.
There are also outposts, on worlds that are less pleasant to live on but have some other value, and in some cases on space stations. People don’t think of themselves as being “from” there: an outpost is somewhere you live for a few months or years while you’re doing a particular job, then move on. That’s not to say people can’t be born there, though it’s unusual; if you’re planning to have a family you probably move somewhere else first. Outposts include prisons, military bases, research stations, mining settlements, and so on.

Economy, Independence and Insurrection

There really aren’t any “low-tech” planets; even the most impoverished colony that wants to build the perfect society will have self-repairing 3D printers and an orbital port, unless they’ve deliberately thrown them away. What you get instead is worlds that can’t afford much in the way of manufactured imports or the latest designs for local production, and then you see where the society’s priorities lie based on where they spend their high-tech resources.
The canonical model of local uprising wants to declare independence. (Changing allegiance to another great power is an easy thing to do after that.) The path to that which doesn’t involve taking on warships means getting control of the local government, ideally in a way that looks convincingly like the will of the people, and then asking the colonial power to leave. So on a poor enough world you might well find that most of the fighters have laser pistols (small and cheap) but improvised heavy equipment (the canonical armoured bulldozer) because importing the latter would have been too expensive.
If an uprising has enough offworld finance, of course, it can afford the full TL11 panoply of frightfulness. But then it becomes obvious that it _does_ have such finance.
Some colonial powers are more inclined than others to grant independence. Warships can blockade a system from interstellar trade without coming near the planet; at that point you really need foreign help to make the blockade too expensive. Actually attacking a planet with shipboard weapons is regarded as a last resort, but landing troops may well be useful. (This is generally done in landing craft rather than as individual drops from orbit, though the Marines tend to favour the latter.)