Re. the pay or play model, I think a combination of the Discourse Subscriptions plugin and trust level 3 may be what you’re looking for. The trust levels have automatic user groups and the Subscriptions plugin can automatically add/remove users from a group based on their payment status.
You can then change the security settings for certain categories so that they are only accessible to the trust_level_3 group and your subscription group(s). This way if a user either pays the subscription or achieves trust level 3, they will gain access to those categories. If they stop paying or lose trust level 3, they lose access.
“Rewarded with some bonus”, if you mean something beyond free access to those premium categories, would need a plugin. Have a search through the #plugins category here on meta, you might find something that meets your needs.