Odoo 11

I am trying to build a e-trading platform to serve multiple companies. use two level odoo structure 

AT master level odoo, the platform can create company, assign the apps to the specific company, such as company A has CRM, HR, email marketing and company B has Project, CRM and inventory.

At the second level odoo, Each company has their own domain and own user management system. No information to share between companies(avoid data leaking), user can access and use app which the platform level assign to them.

is it possible to use odoo to build the two level structure? and Which way I should use multiple instance or multiple database?

Thanks for help