I haven’t work with multi-site a lot yet – I’ll have to play around with it and the add-ons.
a) I believe once the plugin is network activated, you need to activate it on the individual sites, and then go to “Appearance > GeneratePress” on each site to choose which add-ons should be enabled.
b) Interesting – can’t think of how to disable this right now – I’ll have to look into a way of doing it.
c) This is something I may need to change for multi-site so you don’t need to verify it on every site. Will look into this too.