Worm posits a universe of many realities, but introduces an increasingly high energy barrier to reaching those realities as they get closer your own - hence why Khepri could not pop next door to pick up a few dozen identical twins who made decisions like wearing different shoes to the Slaughterhouse 9 fight. Thirty years worth of differences seems to be the approximate minimum amount at which it's actually feasible to access another reality, and even then, doing so too often exhausted the power supply of a shard, the only time we've ever seen that happen.
With this in mind, I rather assumed that Coil's power was so limited - only one "fork" at a time, progresses in real-time, no ongoing communication between forks, provides no peripheral benefits, etc - because it was actually extremely high-cost and involved for the shard. I assumed it was a network permitting the transfer of information between Coil's shard and every other possible iteration of Coil's shard, activated by use and directed by his decisions. When Coil A split himself into Coil A1 and Coil A2, what he was actually doing was transferring information between himself - Coil A - and Coil B, a Coil in another reality who had, at that exact moment, chosen to make the same split into Coil B1 and Coil B2, with the decisions reversed. Should Coil A (Coil A1/Coil B2) choose to "collapse the timeline" and proceed on his own, he's actually severing that connection. Even when "our" Coil died, there were still an infinite number of other Coils out there, ones who'd split off earlier and were still briefly connecting to each other in the quantum bullshit equivalent of Liking someone's Facebook page. Having this be the case also explains Coil's ability to collapse timelines in an unbiased fashion, a "meta-Coil" who is aware of what is going on between connections at all times but does not or cannot share that information - it's his passenger, which we know to be able to guide its host's power-usage in this fashion.
Wildbow making it into a "precog" power - a completely accurate simulation, a sort of multiversal Laplace's demon - is much less satisfying, and doesn't actually seem to allow the power to work as described. For it to work as we perceive it working, both in Coil's interlude and outside of it, his power would need to create two totally perfect copies of the entire multiverse, play out the differences between them based on his decisions up until the point where he chooses to collapse one of them, and then subconsciously guide him down the non-collapsed timeline until the moment of collapse, at which point (and only at which point) it dumps all the sensory information from the collapsed simulation into his head. This is pretty fucking absurd, even before you get into questions or problems like his ability to predict/model unpredictable things (Leviathan, for one) or for his power to apparently mimic every single other information-granting power out there as part of its modelling.
