Sevice Domains and Sub-sites

Hi, I have been test/model site building on Drupal 7, but am planning to build the production site on Drupal 8. The frontpage interface on Opigno shows a menu that goes straight to the catalog and dashboards. However, I need to build in sections for the front-end company website content (organisation aims, concepts, terms of use ec.), a business services section, learning showroom/portfolio display site for the students, learning resources (wikispaces, content & study tools libraries) and three types of courses/levels of membership with different access rights and pedagogical requirements for both students and teachers. 1. Drupal 8 now incorporates the GROUP module, so I have understood that this will obviate the need for separate domains and subsites for the three membership schemes. How could this best be done in Drupal 7 that uses Organic Groups ? 2. How best do I create the other sections so that they show up on the frontpage and menu in order to inform and lead/help customers (students and business clients) through the basic information gathering and signing-up process ? How do we build the wikispaces facility if don't want to use and pay for the expensive Moxtra system? For example, I had though about somehow combining Opigno with Atrium for that purpose, but although Atrium staff thought it should be possible, one techie friend of mine advised me against that. Personally I am not yet familar enough with OG to understand how that might be used and linked up, let alone configured, but I did notice that the GROUP module now has a Drupal 7 release - could this be used instead perhaps. Kr, Chris