Will the AIO plugin allow us to globally activate extensions across all sites in the network (i.e. network activation) or is the only way to do that by installing each individual extension as a plugin instead and network activating those?
Yes, the plugin can be network activated, just like other plugins. However, the settings are saved per site. We have a request make it store settings for the whole network. It's still on our plan.
Yes the second piece of that (making settings store network-wide so that activation of a single component of Metabox AIO means it's enabled network-wide) is what I was looking for. Will just use individual extension plugins for now. Thx!