shopUpz app provides bi-directional quantity updates so you will not oversell. For example when a new order comes from Etsy the app will update Shopify quantity based on the listing SKU vice versa, if the order comes from Shopify shopUpz will update your Etsy quantity automatically.
Sold out listing status is the only exception. Here is what you need to do: When a sold out listing is back in stock please update Etsy listing to active with the right quantity and shopUpz app will automatically update your Shopify listing based on the same SKU.
For any other Etsy listing status you can decide if you want to update the quantity on Shopify or on Etsy and we will update the other store accordingly.