The option 2 would be the correct ordering of child case.
By the definition of class inheritance the child class can use all of the rules defined for a parent class. The Pega Platform supports two types of class inheritance: directed inheritance and pattern inheritance.
Both types of class inheritance allow rules of ancestor classes to be inherited. However, class inheritance does not apply to external classes, even if the class name contains a hyphen.
Out of the two options both can be used as class hierarchy for child case where you can achieve reusability with below configurations.
1. If you use Org-CustomFW-SCM-Work-Order-OrderLineItem --> Child Case, then class inheritance of the "Org-CustomFW-SCM-Work-Order-OrderLineItem " must be Pattern inheritance so that you can reuse the rules from "Org-CustomFW-SCM-Work-Order" parent class.
2. If you use Org-CustomFW-SCM-Work-Order--> Parent case, then then class inheritance of the "Org-CustomFW-SCM-Work-Order-OrderLineItem " must be Directed inheritance with the parent class mentioned.
you can refer the link below to have a better understanding of how class inheritance works.