Do choices affect the Ace Combat 8 story?
Yes, but the confirmed effect is focused on character survival and later story beats rather than completely different main campaigns.
Confirmed explanation
A hands-on mission included a request to spare enemy pilots. Project Aces also said performance while protecting allied units can determine which characters survive into later events.
What is not confirmed yet
The number of endings, decision flags, replay behavior and exact Ace Style thresholds are not known.