Certainly interactors can create aspects of digital stories in all these formats, with the greatest degree of creative authorship being over those environments that reflect the least amount of prescripting. But interactors can only act within the possibilities that have been established by the writing and programming. They may build simulated cities, try out combat strategies, trace a unique path through a labyrinthine web, or even prevent a murder, but unless the imaginary world is nothing more than a costume trunk of empty avatars, all of the interactor's possible performances will have been called into being by the originating author.
I think this is an interesting idea to tackle, that the interactor may feel that they are having an impact on the world but are actually only acting within the limits of what another entity has already created. It creates a sense of false agency, where you may feel that you have control over your choices but are actually only acting within the bounds of whatever you are engaging with.