I think the answer to the question of honing your synopsis to mesh with characters won't be what you expect. The synopsis is primarily there to briefly lay out the plot. Character sketches and world building are entirely separate from the synopsis, even though they'll contribute to the final outcome.
In a book I'm writing, I have about six main characters, excluding the few main antagonists there are. Each one has his/her own character sketch (some longer than others, one actually nonexistent). This allows me to define how they interact with the world around them and with each other.
World development and character development can be done concurrently, but I don't think there's a good way to mesh them together until both the world and the characters have been defined on a basic level. A basic level for characters would include things such as personality, background, motivations, any relationships/affiliations you may know of at the time. For the world, a basic level would include geography (to an extent), general culture (which can be refined later), environments, threats, and politics to some extent. From there, you're able to fine tune the two of them so that they fit together in order to create a full sketch that fills in the blanks that inevitably arise.
There will actually be places where you won't be able to develop a character enough without using the setting.. At the same time, there are parts of the setting that can't be defined or developed without certain characters. This is why it's at least necessary to have the basics so that you can easily fill in holes as you go along.
A decent example of the above (because I feel I wasn't very clear) is from my writing. I have a character for whom I couldn't even come up with a good personality until I had enough of an idea of what roles were still needed in the setting. At the same time, there were major parts of the setting/plot that I couldn't define until I knew what some of my characters were like.
In short, it's possible to make a setting sketch, but doing it from scratch (trying to define the world and characters at the same time in the same sketch) would be highly infeasible. The best route would be to start with the basics of each, then merge them. This is where I would start worrying about character vs. setting. At some point, it becomes necessary to develop both because one will often need the other to be clearly defined.