I think I'm following, but to get clear:
You're envisaging something a bit like your (4) above ie classic "skilled play" but not identical.
Classic skill play involves the notes being, initially, the (hidden) map and key, which the players have to uncover, by declaring actions which oblige the GM to reveal bits of it; once these have been uncovered, the notes also establish what rewards the players are able to obtain by declaring appropriate actions (everything from "We empty the contents of the chest into our backpacks" to "We throw the aardvark we capture into the magic pool of transforming-aardvarks-to-platinum pieces"). This is all locked down, in advance, as much as possible to prevent GM deliberate cheating or inadvertent bias.
Your "skilled railroad" involves the notes being a sequence of events - probably many but perhaps not solely fights - that will be worked through, either literally in sequence or via "node-based" choices, and which the players have to succeed in, with a constrained resource pool, in order to win. Lose a combat and you lose. Or spend too long restoring your resources, and you lose because (in the fiction) the cultists have completed their evil ritual. Etc.
Have I got that roughly right?