So, I'm not going to use the term "agency" here
@clearstream (for awhile I've been using the term "say" for system, GM, and player contribution as I find that is considerably easier to triangulate and discuss), but here is something I'll throw out about your (a) - (c) above.
In Story Now games, all participants have both discrete and overlapping responsibilities. GMs frame scenes and use the rules to do so and to give expression to the obstacles/strife/antagonism particular to the game in question. Players play protagonists and use the rules to give expression to their struggle, to their efforts, to their protagonism.
However, everyone needs to "stay frosty." Everyone needs to have their radar on high alert for a participant introducing stuff into the play space that provokes and can give rise to conflict whether that be strife internal to a particular PC, intraparty where one PC might be pitted against another, or PC(s) vs external antagonism. * GMs have to make decisions on that stuff and introduce content via scene framing, consequences, and give expression to antagonist agenda/motivations (like Faction or Setting Clocks in Blades). ** Players sometimes might say and do something through their PC like "yeah, I'm taking a stand here...what are you (another player through their PC) going to do about it(?)".
If you (a participant in the game) feels like your "say" is being negatively impacted because of one of the above, then you're not in the right headspace. That is not how you approach any participant provoking/challenging/aggressing your character. Your job is to (a) be aware, (b) be open and receptive (try hard to find a way to onboard this and make this provoking/challenging/aggressing moment interesting and impactful so we can all learn something about your character...this 100 % entails not having this super-narrow, evolved, and mature conception of your character early in the game...let the actual play do that evolving and maturing), and (c) , on the rare occasion you can't resolve things through (b), be solutions-oriented if the framing of the provocation/challenge/aggress feels like it needs a little bit of massaging to something that feels more engaging to you.
Players who are in the wrong headspace (who are either looking at play through the lens of "
my character...my matured conception...the game should be about mapping this onto play rather than challenging/aggressing it" or who are looking at play exclusively as an
optimization problem to resolve all stakes and conflict down to as close to zero as possible) might erroneously misperceive these games and these moments within these games as "agency-defying" or something. But that is totally missing the point of the games precisely because you're in the wrong headspace. Through the confluence of this sort of systemization of participant role, procedure, technique, and participant meta/headspace, a type of play and a type of "say" is afforded to the participants that they otherwise would not have available to them. But if you're in the wrong headspace, if you don't understand the rules/procedures (and that includes either disregarding key aspects of the game text rather than incorporating it), and/or aren't observing the play meta...then you're going to have a bad time. And that blind spot (of your own doing) might make you blame that bad time on the game or another participant (rather than taking upon the responsibility yourself).