PikaPower articles (like blogposts in Wordpress) to de indexed
https://flarum.org/extension/justoverclock/frontend-blog
https://flarum.org/extension/v17development/flarum-blog
Are examples of blog implementations that are currently available.
PikaPower have special closed forums / categories
The 1st party extension tags offers categorization attached to permission groups. You can pretty much configure them any way you want.
Similar to previous question. You can have tags that are private to certain groups, or public. You can also make the entire community private, invite-only or fully public.
https://flarum.org/extension/fof/doorman
https://flarum.org/extension/sycho/flarum-private-facade
PikaPower have a an option to pay to get access to the closed section
https://flarum.org/extension/blomstra/payments