Post game bosses/extra bosses/superbosses

I’ve gotten through everything except for the chapter 2s of Temenos/Throné, Hikari/Agnea, and Partitio/Osvald, so I’m wondering about the post game bosses and such. From what I know, there’s Vide which can be unlocked after I complete the crossed paths, there’s Galdera, which I have already unlocked thanks to doing Al’s quest line, and I just need to go to the Gate of Finis, and then there’s the battles against the OT1 party, but I don’t know how to access those. I assume I’ll get access after defeating Vide?

I’ve explored everywhere except for the Curious Nest in the Sundering Sea, so idk if that’s a part of something, but these are the only post game bosses fights, right?

Also, which ones use the whole party like in OT1’s Galdera fight? I assume Vide does, but does Galdera as well? I don’t think the OT1 part fight uses all 8 travelers, but I’d like to be sure. My main team of Throné, Hikari, Castti, and Agnea feels a lot more powerful than the B team, so I’d rather not grind the B team up more than I really need to