For each leave the workflow is defined in the second tab "Workflow" of individual leave setup page as shown below.

Exception Approval - if you want to allow employees to take leaves beyond what is available in their account you can enable this parameter. An exception leave occurs when the leave balance is going in negative

Max number of exception leave - this is linked to the previous parameter and allows you to specify the maximum number of leaves which can be taken, if nothing is specified then there will be no limit to the leaves which can be taken

Request Initiator - The roles which can create the leave request are given here. Multiple initiators can be selected

Approvers - Approver(s) of leave request can be selected here, multiple approvers can be selected and the request will go through all the levels of approvals one by one

Exception Approver - Approver(s) of exception leave request can be selected here

Company Specific Workflow
If multiple company setup is enabled then for system defined leaves like Leave Without Pay / Compensatory Off you can define separate workflow for each company.

If you want to create separate workflow for same custom leaves in separate companies you can use the feature of creating different leaves but giving them the same "Leave Type" which is allowed. The leave short code has to be different.