We have talked some about plausibility. I don’t think anyone has phrased it this way, but it sounds like in blades the player is choosing which plausible outcome will occur on the success. The Dm determines the position (almost an advantage like slider). The effect part wasn’t as clear to me. I thought the player set the outcome which sounds a lot like effect to me?
The player states their goal for the action. "I want to dash across this courtyard without being seen." The GM considers all the relevant factors and then says something like "The courtyard is pretty big. If you want to remain unnoticed by being as quiet and careful as possible, then you'll only make it part of the way. I'd say your position is Risky, and the Effect would be limited."
This is the GM taking the players goal and saying that they can only achieve part of that goal with a success. Their Effect will be Limited. I think one of the things to notice here is that the GM is gauging everything based on the player's stated goal.
The player has a few options at that point.
1) "What if I just run full speed and try to get across before anyone sees me? So I'm less careful, but going at full speed. What then?"
The GM might respond "Okay, so it sounds like you're trading Position for Effect. So the chance that you're noticed goes up, but you can make it all the way across. I'll say Desparate Position, Standard Effect. Go ahead and mark an XP." The player has made the action riskier....they're more likely to be noticed, but they can make it all the way in one action. Standard Effect means you should achieve what we would consider a full success. The player also gets an XP for a Desperate action.
2) Or the player can say. "Okay, Risky/Limited. I'll spend 2 stress to Push for Effect. That makes it Risky/Standard, right?" Spending 2 stress allows you to either roll an extra die as part of your roll, or allows you to increase the Effect by one stage on a success. In this case, from Limited to Standard.
In this case, the GM says, "Okay, yeah....if you Push for Effect here, then it's Risky/Standard. You can make it all the way across and you can stay pretty quiet about it, but it costs you some real effort."
3) Finally, the player may have other factors that they want considered. So they may say something like "Limited Effect? Well, I took a Light Load specifically so I'd be mobile for a situation exactly like this. Do you think that's enough to give me a shot at Standard Effect?"
The GM would consider this, and decide yes or no based on all the relevant factors. If it was me, I'd say "You took Light Load? Okay, yes, then I think you're prepared for exactly this kind of fast but silent move. Go ahead and roll with Risky/Standard."
4) The player could accept the initial statement of Position and Effect as Risky/Limited, knowing that a success will only get them partway across the coutyard, and they'll likely need another action to make it the whole way.
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The player has various ways to provide input on the process. The GM does use their judgment to set the initial Position and Effect, but these are based on the player's stated goal. Then, once established, the player may use resources or negotiation to alter the Position and Effect, and the GM is bound by this. Whatever option from the above happens, the Position and Effect are finalized and agreed upon before the roll is made. The player can always decide not to proceed once it's all been worked out.
Then, based on the actual outcome of the roll, the player and GM discuss what happens, with the GM having final say. Very often, the outcome may be obvious based on the established fiction and the outcome of the roll.