We are currently running our website on Wix.com and will introduce the paid membership, where the paid member is only able to access to the contents.
I m wondering if any integration is available that the access to our private Discourse form will be given only a certain member group for the paid users under Wix.com membership management system.
To answer your question, we currently do not have an included Wix-integration system, however, as Discourse is fully open sourced, you could change that by changing the code and forking the Discourse Subscriptions plugin which is soon-to-be an official plugin and is more than stable to use for communities.