Hello Roberto,

You can refer below mentioned document about payplans workflow.
https://stackideas.com/docs/payplans/administrators/welcome/payplans-workflow

Using PayPlans, you can restrict user to read article without paid for the subscription.
# If you want to restrict user to view the content of article then you can use PayPlans Content Acl app. Using this app you can restrict article as well as category also.
Check here : https://stackideas.com/docs/payplans/administrators/apps/content-acl

# If you want to show/hide some block of article then you can use Content Hider plugin.
Check here : https://stackideas.com/docs/payplans/administrators/legacy-documentation/joomla-article-content-hider

# If you want to sell each and every article but don't want to setup multiple plans in payplans then you can use Content Seller app.
Check Here : https://stackideas.com/docs/payplans/administrators/legacy-documentation/joomla-article-content-hider

Regarding Discount, Currently in PayPlans discount can not be apply as per category. But as you will restrict category as per specific plan then you can create discount coupon for that plan and setup accordingly.
https://stackideas.com/docs/payplans/administrators/discounts-and-referrals/discounts

Let me know if you have any other query and correct me if i have misunderstood.