From my pont of view, to answer your fiorst question, one poster should have just one member of Vanguard, and then can introduce secondary characters, like the B team meber, Quantos, Eddie etc. Thw writing about them should regard their interaction with the story in the main issues, while everything else should be put in solo threads.
For the second question, I think everything that has to be adressed by Vanguard, sooner or later, it could saty in the main story, while what regard just the single character should be in solo threads. For example, I put the dialogue of Euro with Saros in the epilogue of last story because the future actions of saros will have an impact over Vanguard, while I have kept Arturo Ghiorzo, a new nemesis for Euro, just in my ongoing solo thread, because I plan to have him to fight just Euro, without involving Vanbguard in it.
