It came up in a game of mine a while back of who declares swarm tactics in what order. His Vader had swarm and tried chaining to two others to all get PS9. Depending on how he chained though, I could either do two PS8, and two PS7. Now it may not sound like much, but he had a PS7 pilot on the board and if I chained at PS8, then I would have had 3 ships shooting before his PS7, but if I chained a different way, I could have had two PS8 & two PS7 which would have been four ships vs three ships shooting before. How HE chained directly affected how I was going to chain since his chain and how he fired changed how I was going to set up my firing schedule.
So who chains first? Is it the person with iniative?