Does OCI administrator role cover the privilege for IDCS administrator role ?

Previously, when we have a separate instance of IDCS and OCI. IDCS administrator role and OCI administrator role are separate.
After that, IDCS has been merged to Identity domain and become a part of OCI.

Our client would like to understand the scope of these two roles.

For example,

• Does OCI administrator role cover the privilege for IDCS administrator role ?
  For example, It seems the OCI administrator role will be able to add/remove users from group or grant/revoke access.
  Is there any other scope in identity domain that OCI administrator role can perform ?

• Is there any operation that IDCS administrator role can perform, but OCI administrator role cannot perform ?