There are two main ways you can set up and organise Case Management for complaint handling.
Case Types
All complaint cases are raised by submitting a form. In your forms you set what type of case should be raised. That means you could have a single form that is used for all complaint types, or set up different forms for each one.
If you use different forms for each type of complaint, they could raise different case types. For example, you could have a form for "corporate complaints" that raised a case called "corporate complaints" and a separate form for "service complaints" that raised a "service complaints" case type. The two case types could then be configured individually, with their own SLAs, users, notification settings etc.
The most common implementation is to have a single form for submitting complaints, as described in Making a Complaint. This will raise all complaints cases as a "complaint" case type, which would all share the same configuration. Case subtypes are then used to categorise them.
Case Subtypes
The subtypes you can use to categorise your complaints are set up in the Complaint Case Type Configuration. You can create as many as you need.
Most organisations have a central team that first reviews complaints (to decide whether they should be classed as complaints, or as an enquiry/service request), and then assigns them a subtype using the link while Working on a Case.
All of the dashboards used to report on complaints can be filtered by subtype, so you can see information relevant to the service that is being complained about.