Hello Santosh,
there are 2 case for system configuration
backend system as ECC 6.0 EHP 4.0 than Document Like PR , PO , confirmation and contract will get created by Xml interface for this you need to activate configuration of E SOA. which may or may not need PI depend on ECC system support pack level.
if you are making backend system as ERP_3.0, These will be no impact and The PR/PO will created by RFC and Confirmation will be created By Idoc interface.
We have done second setting for one of out rollout.
Thanks
Sharad