Twilight and KC are both about an apocalyptic future (not an entirely original idea itself). That's pretty much where similarities end. Twilight was actually planned as a crossover type event.
The story is structured so that there is a central "core-narrative" which in this case is the tale of the Twilight of the Superheroes, taking place at some point in the not too distant future, say twenty or thirty years. Around this there is a sort of framing narrative, a device which links these hypothetical future events with what is going on in the DC continuity at present. This device provides the sort of interface between the fairly self-contained story of Twilight and the numerous fairly self-contained storylines and continuities of the DC Cosmos, and it is achieved as follows: we have agents in the future who have managed to send a message back to agents in the present day DC continuity, urging them to warn the superhero community of the terrible future that is possibly waiting for them, and to avoid it if at all possible. (This is not without its own ambiguities, as we shall hopefully see, but it provides for the moment the easiest conceptual handle with which to grasp the mechanics of all this.) Thus, the agents in the present set about reaching various superheroes in the present and delivering the warning. Some of those who are warned heed the warning, and make decisions in their current doings and lifestyles that will hopefully avert what is to happen in the future, even though this is by no means definite. Others will ignore the warning and carry on with what they were doing, which of course has some relevance, even by default, to the outcome of this horrific Götterdümmerung waiting in the potential future. Some of the superheroes affected will perhaps not be reached at all, and thus remain ignorant of the whole thing, although this, too, obviously has relevance to the outcome of what will happen in the future. I hope this makes it comprehensible how I hope to solve the problem of writers/artists who don't really want to involve themselves in the storyline: even if they choose to have their characters remain oblivious to everything going on, or to ignore it, their actions are having an implied relevance upon what is going on in the crossover book while at the same time what happens in the crossover book down the line in the future will be seen as having a direct relevance to how those characters are perceived in their own books. Knowing the fate of characters in even a potential future lends them a sort of poignance which is very important and which I'll take a few moments to discuss.
Say what you like about Alan Moore but the guy's notes were near essay length , he fleshed out the plotline , ideas, character placements. Christ the only thing he didn't add was individual dialogue and background description !