What comes first the chicken or the egg? Or, character or plot?

Hey guys would love some advice on this:

1.  I am trying to write a novel with 8 POV characters in third person. Each POV tells a different storyline through the character’s arc, but all the storylines intersect with each other, and the reader should be able to put all the pieces together, even though the story is non-linear and the characters don’t have all the information. E.g, ASOIF, The Broken Earth Trilogy, or Stranger Things.

2.  The different POVs will explore different themes and genres, like politics, dark romance, horror, adventure, coming of age and mystery. 

3.  There are several side characters and sub plots. 

4. I have a general log line describing each POV, but not sure how to go deeper with their plot. 

I have tried creating a massive excel sheet with all my POV character storylines for different acts, so I know some POV characters better than others. To help finish (or more accurately start) my novel, what is the most productive and best use of my time? Is it, understanding all my POV characters first (their wants/needs/ internal conflicts) or understanding how the different storylines can link and work together for a coherent story?

My instincts say I should focus my efforts on character first, because even if I work on the general storylines first, when working on the characters and their motivations, it might come into conflict with the way I have already set up the story. 

But would love to hear what you guys think