From Non-encumbrance to encumbrance environment?

We have basic financial modules, AP, PO, AR, GL, PA. We are currently in a non-encumbrance environment.
Our Production went live two years back. We have many on-going POs, Requisitions, AP Invoices and Projects.

We plan to enable encumbrance accounting using a non-integrated Project budget option.

Based on experience from anybody here, any issues we can encounter especially from outstanding Requisitions/POs and AP Invoices. Will non-Project Requisitions/PO or AP Invoices be impacted since it is a non-integrated budget.