Unfortunately that was not possible to achieve this at this point of time.

By default you can configure these post limit restriction from the profile type, but this is only a few stuff can set the limit for the user :

For example :
- Conversation limit
- Group creation limit
- Page Creation limit
- video creation limit
- Event creation limit
- Albums creation limit
- Photo creation limit
- Report creation limit

Regarding the group, it actually based on the category what you configure the limit instead of the single group, currently only available to set following limit restriction :
- Total Photo Allowed
- Total Daily Uploads Allowed
- Total Files Allowed
- Total Videos Allowed

Thank for your respond.
Could you move this question to request feature category?
Thank you.

Sure, thanks for understand.