Aspiring Lurker (He/Him)
This is a great question and a great way to focus conversation. Thanks for asking it.
Thanks for answering it seriously.
I have no issues with your descriptions of agency types, so I'll move on ...
How do you think "authorial choice" and "participant choice" relate to one another when you've got competing interests and rules/role constraints that bind or deny authorship rights?
Put another way, the GM can't do x because system or built-in constraint (a players move/feature says thing n happens; GM doesn't get to ignore it or erect a block that negates it) says so. The player can't do y because system or built-in constraint (the GM has erected an obstacle that requires overcoming a certain fictional positioning - say reach advantage by the obstacle - before the player can close to melee...the player doesn't just get to ignore that and close to melee).
I would say "participant choice" is different than "authorial choice" because when you're writing a book, you don't have competing interests and system architecture that both constrains possible fiction and mediates outcomes.
That's reasonable. I guess I was thinking about corroborative/cooperative authorship, or possibly playing in a band (I've done both). The player is the author of his character, using the game system at the table (I mean, it's no use to bring a FATE character to a D&D game, or vice versa, right?). The entire table is generating a story (or a story is emerging from the entire table playing a game), and the player is directly responsible for a portion of it, centered on one character. I'm thinking this through more or less right now, but I guess I'm at a point where Player's authorship of Character is absolute, within the rules of the game, until/unless it interferes with another Player's authorship. The GM has (mostly) authorship of the world/setting, and I'm not entirely sure where the boundaries are between that and Player authorship (or, I'm not sure I can elucidate them; I think I have a decent nonverbal feel for them, though).
I'm not sure I've answered your question about constraints and bindings on authorship rights.