Once again, in both of these instances, I need to ask myself "what am I doing here? What do I want this part of the game to be about?" And then I frame that in terms of the group. Outside of this group at this time, is anyone else ever going to interact with these locations?
So if I'm running a scenario on a remote island, and I have a criminal and a noble character (hey, one of them is a scoundrel, the other's a princess), I ask myself: what do I do with this remote island to make it interesting for my group? What is my group going to want to do here (beyond get off of it, of course).
So the criminal might say "hey, this is a place that's never heard of my syndicate. But there are people who are criminals here, so that's an opportunity to establish my group in this distant land." And that character might want to integrate with that part of the culture, do some work for them, buy and sell some things and so on, so that they can expand the reach of their syndicate in the future. Plenty of opportunities for quests there and built in plot hooks! And it again makes that choice matter.
The noble might want to get involved with whatever power structure exists on the island. Who runs things? Once again, they might use a very different approach to try and get involved with the powers that run the island. And again, that's the choices the player made for their character shaping what they want to do at the same time as it gives the GM options about what to do next.
And as far as the prison, I can't think of a better place to put members of the character's crime family than a prison. As you're designing the factions and power bases, you know what one of them is. For the noble, I'm sure there might also be some disgraced nobles in the prison that make up their own faction and the player might become a part of. Once again, the players have built in plot hooks that are going to get them moving without you doing a thing. Maybe there will even be tension between the two characters.
In both of those cases, you're making what the players did in choosing their backgrounds matter and linking them to the game. You created the remote island and the prison, so you got to choose who was there. Making them align with the characters in the game makes it more interesting to me if I'm one of your players. In a lot of cases, the way you're describing the game is going to keep me at arms length from getting involved with it. And maybe that's what you want to do, having a more "this is the world, and you're just a small part in it," is an approach that it seems a fair number of GMs like to do. I've played in a lot of games like that over the years and they make me say "I'm dropping into this world and then I'll leave it," rather than being a real part of it.
What it does for me is make me say "I wish I was in that party that's more interesting than ours." I think it's been said a number of times already, but it's always possible to say "no" as a GM and have it be logically consistent, since you made up the world and put everything in it. I'd just ask how it's better world building to do that as opposed to building it around what your group does with their characters.
I really do get how a lot of the things I'm talking about are more based in other rule systems, but nothing I'm talking about breaks any existing D&D rules.
