I know how it is, trying to figure out a key point to the story, and how that can stall writing until figured out. Best advice is to pick an approach, write it, and if you don’t like it, change the approach and try again. If you can, focus on a few key scenes so you don’t have to write the epic novel only to trash it.
I had a similar dilemma stall my potter fanfic for well over a decade, still gives a bit of nerves when I think about it. Consider “A” as a small party, “B” is everybody else. I segregate off “A” from “B”, to the point that “B” considers “A” as totally dead. (I’ve already added some foreshadowing for this bit… still coming.)
What I had wanted to do was to show everything purely from B’s POV, because that’d be maximum mystery, also read as a horror as plans keep failing and Voldemort keeps advancing. However, it’d also make the climax/resolution read like the biggest deus ex ever, it’d rob the reader of the schism and conflict that’s brewing in A, the actions of “A”.
If I went full “B” first to climax, “A” to climax, every scene has to be built up whenever there’s B/A crossover. Not to mention the head-scratching by the reader to keep things sorted in a multi-million word story.
As I’m not writing a mystery, this time around, I’m going to mix the POVs together, like I’ve been generally doing for most of the story anyways. True, while it’ll still seem dire to B, the reader will see A’s side … less mystery, horror aspect still there, but at least I’ll get it written (plan to anyways)
Nothing more horrifying than an unfinished WIP!