Set up of Different subscription plans for different product

How could I set up different subscription plans for different objects in the app. Let's say have different courses.

You can build that functionality by adding plan IDs to your courses and then creating subscriptions for them accordingly. All the payments code is wired up with Pay, so you can use that. https://github.com/excid3/pay

You'll also want to modify the subscription show page to list all the active subscriptions since you'll have more than one.