7 - Can't update page titles
OK! After going back and forth between var_dump's, installed modules list and hooks, I discovered that the ONLY hook that will update the page's tags is hook_metatag_metatags_view_alter(&amp;$output), in which something like this needs to be done:

$output['title']['#attached']['metatag_set_preprocess_variable'][0][2] = "Custom title";


My n00b diagnosis is that this hook is called right after the last Metatag module's function that rebuilds the metatags from scratch, and therefore it's the only one that matters.

Hope this will help others! :)

~Steph