Some of the Sellvia products are the same as my Premium products. Should I remove these Premium products and import Sellvia products instead?
Replacing the products is not necessary. If someone buys a product that you previously imported using the Premium Products add-on, you will still be able to order and ship it through Sellvia.
However, if you want the Sellvia product page design and the Sellvia price, you need to re-import the product using Sellvia.
Note. If you want to keep the option of shipping worldwide, do not replace Premium products with Sellvia products. Sellvia products do not have AliExpress product IDs necessary to order from AliExpress.