No worries.Sorry to take so long to get back on this.
In the abstract, yes, but I think some games will push back in various ways.I think that the methods you are describing, divorced from mechanics that support them, can be applied in a general way to just about any RPG. Would you agree with that? You said that Story Now is not dependent on mechanics, so is that what you meat? That Story Now elements can be used in any game?
First, I think you are taking a RPG to be defined by its action resolution mechanics and its PC build mechanics. But most RPGs also include GMing advice. Consider AD&D's GMing advice (whether Gygax's original advice or the rather different 2nd ed advice), for instance: running AD&D in a "story now" fashion will require ignoring the bulk of that advice.
Second, not all RPGs have devices for signalling by way of PC build. Again in relation to AD&D, I've stressed this as a contrast between OA (PC gen that yields thematically-laden PCs pretty tightly bound into an evocative setting) and trad AD&D (PC gen that tends to yield PCs with few or no hooks - thieves being the obvious exception for the main classes, and perhaps some of the more boutique classes like paladins and monks - but an all-thief party is far more likely than an all-paladin or all-monk party!). The same contrast can be drawn between RM (detailed PC building that is player-driven, allowing signals to be sent) vs RQ (much more Traveller-style simulationist random rolling in PC build, so that the build of the PC doesn't necessarily tell us much about what the player wants out of the game).
In my 4e game, I required each player, in building his/her PC at 1st level, to include in the PC's backstory (i) a reason to be ready to fight goblins, and (ii) a loyalty. These kickstarted the game and have generally remained important (whether in original or developed/mutated forms) throughout the campaign. That is something I added to 4e.
Third, action resolution mechanics can cause issues. RM, for instance, doesn't remotely support "fail forward" - which means that consequences of failure can lead to scenes bogging down unresolved, which is the nemesis of "story now" play. In my experience, the practical solution is that players gravitate towards spell users, who have the capabilities (via their magic) to overcome these moments of bogging down. RM's healing rules are also a big issue. As I posted upthread, I think 5e's "bounded accuracy" might be a source of problems, making success rather random relative to the commitments expressed via PC build and play (because anyone can succeed and anyone can fail).
Fourth, some systems give players very powerful scene-reframing abilities (divination, teleportation, starships in Traveller, mind-control spells or diplomancy, etc) which mean that instead of the GM's scenes provoking choices which speak to the themes of the campaign, the players are incentivised to squib on the scenes by reframing them. Which, in fiction, makes sense - why wouldn't a rational person just cast charm monster on the giant king? or use commune to solve the mystery? - but at the table deflates the drama.
Of D&D editions, my feeling is that 3E is probably the least hospitable to "story now" RPGing because of issues (2), (3) and (4): very generic PC building, and with the potentially interesting stuff like prestige classes (i) watered down thematically from what they might be, and (ii) strongly gated behind GM discretions; action resolution that is almost the antithesis of "fail forward" and very strongly favours expedient choices, often bleeds over the boundaries of "scenes", and is often rather intricate to boot but without that intricacy correlating very strongly to in-fiction elements of the situation; and, combining with the previous stuff, many powerful player-side scene-reframing abilities.