A little details of my current situation:

The company I'm working in
- is in the process of migrating from OpenERP v7 (community version) to Odoo v14 (community version) now. 

- is entering the new financial year starting 1st June, 2022.

- have decided to change the inventory valuation methods from a mix of Standard Costing and Average Costing to FIFO starting 1st June, 2022 (expected to go live with Odoo 14 on June 1st)

Questions:
1) Can I just change all my inventory items to FIFO Inventory valuation methods after migrating all data from OpenERP v7  to Odoo v14? What are the consequences? Will Odoo v14 auto pick up the purchase price of quantity on hand items?

2) Do I have to set my all Quantity on hand items to zero. And create the Quantity on hand items in Odoo v14 based on the purchase price? (I did some research and found that this method is suggested for SAP users)

Thanks in advance.