Grendel_Khan
Hero
Just so I understand:
Using The Mandalorian episode "The prisoner" as an example, the GM would set/roll up the scenario (recover a prisoner for a transport) and the players would decide on their approach and detail (cut their way in and skulk) and the engagement roll would define their starting position (in this case, they were good at first) but aside from that nothing is defined?
Yes. Just to clarify, the engagement roll can let you hard-frame the PCs into a specific moment during the job—they're inside, outside the cell, and a security droid shows up or an alarm is tripped.
Did the GM define that the ship was crewed by droids, or was that established during play? The layout of the place, the kinds of security, and all of that is based on the results of rolls and the conversation?
You could establish the droid crew ahead of time, as something the PCs learn when getting or researching the job. Could maybe do the same for layout, possibly making one or both of those details part of the engagement roll result. But the emphasis is on what the characters know, rather than what you've established for yourself, and then hidden, to be revealed during play. Most of the game world doesn't really exist until they encounter it. I know that sounds like a lot of RPGs, but again, it's a matter of degree. If you've set up a ship's deck plans and are using that to guide the players—so you know how many doors they have to get through, and/or how many potential enemies are behind those doors. Ideally you define things as loosely as possible, so that with a rolled consequence or proposed Devil's Bargain you can say that actually there are humans overseeing the droid crew, and that they use the droids because the ship is a transport or storage vessel for powerful Sith artifacts that tend to influence nearby living things, and the prisoner is being used as a test subject to see what prolonged exposure does. Or on a later miss, once that stuff has been established in the moment, you might say the prisoner is there voluntarily, trying to marinate in the dark side, and they're hostile to your breakout attempt.
I don't think there's a concrete sense of how much or how little to prep, though.