Hi Anthony,
You could not use transaction ME25 when you have release strategy in place. When creating a purchase order with transaction ME25 the system first creates a purchase requisition. Then after the supply source has been assigned it is converted into a purchase order. This is the reason why
a strategy for requisitions is effected. You will have to save the purchase requisition, release it and assign the vendor.
Yes, those transactions are used to convert the PR into PO.
I hope this is useful.
Best regards, Gordon