When you're thinking about parallel stories and writing them, how do you keep them disparate so that you don't have characters from one story overlapping with another story...
This is a balancing act I perform when writing big, long books, because a lot of times for narrative reasons, it is better to write them "this set of characters, then the next set, then this set, then that", and go back and forth, but a lot of times, for continuity of theme and character building, it is better to write them straight through, right, that one character's throughline, so you make sure it has an emotional arc to it. And the longer the book gets, the more delicate that balancing act gets, right?
So on a Stormlight book, I usually split the book in my head into three parts, like I write a trilogy of books, and then bind them together as one, with a short story collection making up the interludes and things. And I usually would go, alright, part one, Kaladin from beginning to end of part one. Part one, Shallan from beginning to end of part one. Now I will weave these chapters together and I will read through for theme and make sure that the pacing is working, because the pacing and tone can really get messed up when you're doing that.
Fun story about that: A Memory of Light, I did this with some of the things, and I was weaving them together for the prologue, and two of the things I was weaving together, was characters getting engaged, it was the ladies making a bridal wreath to give to Rand, and the other was the fall of Caemlyn and the people who were trying to live as things were happening there. Not to go into too many spoilers, but it was a really dynamic action sequence, with a lot of terrible things happening, and when I wove those two together, the tone whiplash was terrible. And it was like, one of the worst parts of the book was "here's a happy thing where we're gonna get engaged, now this person dies, then we go back to this happy thing". *crowd laughs* So I had to yank the engagement sequence from the book, because there was no tonal place in that novel where it could go that it wouldn't do that.
And so you run into that trouble, but I think that with the longer books, what you're noticing, keeping the characters' throughline consistent is the more important factor. It's a lot easier, I think, to fix pacing and tone by where you move the chapters and what you cut out and what you add in in revision.