There will be different procurement processes like Standard PO, Framework PO, Services, and STO... but do understand that the "Manage Purchase Order" app will support only the standard PO document types or Z document types created with reference to standard PO document type 'NB' without changing parameters. In this situation, you have to go with the "Create Purchase order" app to create purchase orders for other processes.
This blog will give an overview of all standard functionalities provided by SAP from Logistics perspective which we might have overlooked during our regular practise.