App structure and design pattern

Scenario: in general application for bussiness based on stack ror + angularjs, ror will be only for API purposes and angularjs naturally for frontend. We can actually specify two "big" apps: 1.Aplication "X" will be for customers and based on small "apps" or "modules", for example there will be a module/app for customers like managing shops, their inventory etc, and another module for service workshops and so on, so we can divide that one big app to 5-6 smaller.

2.App "Y" for managing customers accounts in term of checking billing, reset passwords or some another custom stuff managed by admins.

Question: How would you design RoR app structure and files in repository? I mean one big app with several mountable engines of app X and app Y, and one repo ? Or separately two apps X and Y and two repositories ? Please consider case when team which will be developing app X should not have access to repo of app Y.