@hawkeyefan once the initial content or path has been determined how much continued creative input does the player have outside of their traditional character actions?
Can they expand more?
Yes, very much so. Almost all of the "quests" or goals that the PCs have strived for have come from something the players wanted in some way. Yes, I had input at different points, but it's almost always them deciding what to do, or responding to the dice telling us.
For example, the Beast in the forest from the Ranger's background kidnapped a young child from a hunting party. This was something I decided would happen as the result of a die roll made at the start of Spring. Each season, you make a roll to see how established threats progress or not. The Beast's threat progressed, so I decided the next step was for it to steal a child. It actually had some minions do it.
They managed to recover the child before the minions could get it to the Beast. Now, in my head, I had some ideas about why the Beast may want a child... but I wasn't committed to them. One of the players, I think the one who played the Lightbearer (a sun cleric), made a Know Things roll and succeeded, so I was prompted to tell them what was special or different about this child than others. So I explained that the child had bright green eyes, called "Forest Eyes" by locals, which hints at fey blood in their family history.
The dice play a big part at times in when information is established, and how.
Also, another fundamental element of play is that the Steading Sheet lists many improvements that can be made to the town, and all the things needed to make such improvements. So at any point, if the players aren't sure what to do, or don't have any pressing matters, they can always pursue one of the improvements. So for example, the impriovement of having a herd of horses requires building a stable, which means you have to obtain X amount of lumber, and then the horses, and a trainer. So all of those elements can lead to an adventure on their own.
There's no shortage of things to do that the players can select, if they don't have something more immediate to deal with.
So, for instance PCs use a map they acquired to seek an entrance to a long last tomb but say they fail that skill challenge to progress the story
(a) The traditional response would be players would have to think of an alternative way of finding this entrance via DM decides;
(b) The modern approach would be, instead of an outright fail resulting in a No, the DM adds a cost to continue, the Say Yes, but approach; or
(c) The players provide creative input for a path forward which the DM must accept as having a reasonable chance of success by letting the dice decide.
Is (c) on the table as that continued creative player input?
EDIT: And if yes, do the players amongst themselves decide which input will be established by vote/unanimously, the table (including the DM) or just the first person to come up with an idea?
There are many ways you can handle this. There's no "story" in the sense that if the PCs don't succeed, the game just grinds to a halt. There are always other things to pursue, and as GM, it's my job to make sure that interesting things happen as a result of a failure. The results of a roll should never be "nothing happens". So if they fail to use the map to find the tomb, that means I introduce a complication of some sort. It means the situation becomes dire or more difficult. It doesn't have to mean "you don't find the tomb, game over".