quick question about speed caps for Firefly’s TEAM…

I’m planning on running a Firefly, Harmony Trailblazer, Ruan Mei, and Gallagher team comp. I know what speed I want Firefly at, but what about the others? I’m pretty bad at builds and don’t understand a lot of things, especially speed. I’m going for 210 speed on Firefly in her ult form, cuz I hear that gives her 4 turns with it (not sure if that includes E2, which I’m going to get). my speed stats are all really bad on my characters cuz I don’t understand it, but I don’t wanna mess it up for this team, please help 😭😭