To me it seems that most of the fiction and trajectory of play is coming from the GM.
As you put it earlier: This is not, at this point, something I want to die in a ditch over; I did, however, make the offer, so here goes (from I hope a much less angry place than I was in a few months ago):
I agree that the setting and the NPCs come from the DM.
I disagree that the trajectory comes from the DM. Everything arose from decisions the PCs made, right to their being in Pelsoreen. I might have mentioned earlier: They were kinda at loose ends, and found out an allied NPC where they were knew of teleportation circles and was willing to move them around; the players asked if they could go to Pelsoreen--which was not on my list of places they could go, but which it made no sense to be unavailable.
I should probably get my notes--though I don't expect you make a lot of distinction between "DM decides beforehand" and "DM decides on the spot" (I expect the "DM decides" part is what matters to you).
I think that some of what you describe in your earlier post as "RPG-ing as puzzle-solving" was the DM providing information to the players. I specifically remember wanting to make sure the PCs knew about the Masked Ones' weaknesses before encountering them. I occurs to me that when you say that, you usually mean the DM is the puzzle, not that there's a literal puzzle in the fiction.
I had placed the Cracked Shields in Pelsoreen--they're in my notes. OTOH, they came up because the PCs asked Jorly about them; had the PCs not asked, I would have put them in a pocket--either for some future thing in Pelsoreen or to use elsewhere.
I'm pretty sure I don't believe the DM figuring a small child wouldn't be able to place his village on a map, and really having a pretty naive outlook in general removes player agency. It seems as though you think a player should have been able to roll to see whether Turlk knew geography? That doesn't seem right, and I have a feeling I'm misunderstanding something and therefore violently misstating your meaning--apologies, if so.
The temple of The Joyful had been established as existing the previous session (I think). The info-dump the PCs got about the orcs ... yeah, that was DM stuff.
Deciding Rask (leader of the Cracked Shields) didn't like the Masked Ones--DM decision; likewise, what comes up later about members of the tribe having a vendetta against the Masked Ones. The decision to recruit the Cracked Shields to fight the Masked Ones, though--that was the players, all the way.
Oh--the Masked Ones themselves: When Joybell's player decided her village had been wiped out, I asked her to describe the ones who did the wiping as Masked Ones; she could have said no--it was just an idea I had that was actually about stuff that showed up later when the PCs went and destroyed the Masked Ones' Forge.
I'm pretty sure the decision to go to Black Irnod was on the PCs; I controlled him as an NPC, I'll grant. I expect that since that was freely roleplayed, you probably don't think the PCs had any particular agency, there.
The bit where party members tried to do stealthy/sneaky/con-artist things in the House of Masks: There were actual mechanics involved, there (let's not turn this into a discussion of Stealth in 5E, eh?). It just happened that the hive-mind things had all sorts of advantages (as well as Advantage) on Perception checks. It occurs to me that this might be an instance you don't object to the DM narrating events, since the PCs didn't win that particular contest?
The fight between the party (with help from the Cracked Shields) against the Masked Ones was a D&D 5E fight. I expect you think such fights have a given amount of agency, and that this one is no different.
If I've misstated your positions somewhere above, I plead ignorance; I intend no offense.