Payroll Elements and Costing setup for Projects actual costing if third party payroll is used

Summary:

We are implementing oracle Time & Labor, Projects modules but our client is using third party systems for Payroll.

Projects actual costing needs to be done is oracle only.

For doing projects actual costing in oracle for client who is using third party system for payrolls:

Do we need to setup payroll elements in oracle ? What all types of elements will need to be setup (earnings, deductions etc) ?
Do we also need to setup the pay element costing?

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