Drupal fieldsRevealed

Common fields

• There is no concept of 'common fields' for any content types. • Any fields, that you have created previously and want to use for any

other content types, will act as unique field attached to that content types. And you need to configure such fields for each of the content types 

• However, using views, you can set a format type

Sub content type

• There are two ways to relate a content type to the other • Using entity reference • Or using hierarchy of node relation  -- there are modules available,

using which you can define the relation between two or nodes.• Using 'inline entityform', you can display a node form of one content

type in the other. 

Access levels

• Using 'Content access' modules, you can set access on individual nodes or for a content type. 

• You can use 'user relationship' module to define a relation between users and can configure the access using the module. 

• For specific features like "visible" / "visible on request" / "visible and need request", you will need to build a custom module using User relationship module API and extend it the way you want.

• For any other permissions/access, you need to implement hook_permission (Drupal7) & hook_entity_access (Drupal8)

Reporting

• Using flags, abuse and fivestar ( along with voging API) modules, you can set up rating & reporting system.

• This also serves as feedback from the users.

Localization

• For localization, you can enable the inbuilt 'locale' module and also use i18n modules. 

• To make it specific to author's language, you will need to do some customization which will identify node author's preferred language and allow him/her to translate the node in the other language. You can also provide a drop down box on the node form for the same.

Performance

• In all cases, you should use different caching techniques like authcahe, varnish, memcache, boost etc. 

• Hosting your site on a good server with good conflagrations will allow you handle large traffic & requests.