The plot question had me thinking now! If I have, say, approximately 800 worlds halfbuilt in my head and thrice as many characters with their own personalities, lives and backstories that weren't really created around a plot of any kind but they're here I guess, would you say it's a better idea to try and hammer something out of what I already have or scrap it and start over, This Time With Plot? Should I try to shove those existing things into that new plot, or bake everything from scratch?
There are a lot of potential worldbuilding pitfalls a fantasy and science fiction writer can stumble into. One of these is making your story boring by overburdening it with too much expository worldbuilding. This, in turn, is often a symptom of a writer who spent years and years practicing worldbuilding—but not much practicing the actual craft of writing. - Brandon Sanderson
If you have 800 worlds and 2400 characters but zero plot, that’s an issue. The plot of the novel is the novel. Everything else simply improves upon it.
Let me ask you this: when you bake a cake, do you start with the frosting and sprinkles, then throw the flour, egg, and cocoa on top of it, hoping that a cake will form? No. That’s a big ole mess. You make the cake first, then you apply the frosting and sprinkles. Because at the end the day, it’s not a cake without the actual cake. Gotta bake it first before you can decorate it.
Put your focus where it belongs: on the story. If a handful of your existing 800 worlds/2400 characters work for the story you created, cool. If not, such is life.