Hello @blaz,
Great question!
Since Klaviyo does not have a direct integration with Wix, the integration connecting Wix and Klaviyo currently suggest it is a custom built one. Because these two are connected in a custom manner it would not interfere with your goal of migrating and integrating with Shopify.
From my experience although it would not pose any challenges to have both the Wix site and the Shopify site connected while you are still in the process of migrating, I suggest setting up the Shopify site fully prior to integrating Klaviyo to the site and disconnecting the Wix connection soon-after. I recommend this method of migrating as having both Wix and Shopify connected at the same time may cause issue such as signup forms appearing on both site, metrics and events not firing correctly/accurately, or profiles not being collecting accurately.
Klaviyo works best when integrated to a single ecommerce site/platform at any given time. Having two ecommece sites integrated to a single Klaviyo account for a short duration such as a brief migration period would not cause any issue, but for extended periods of time may cause problems in how your data is collected.
If you need, I’ve also included our How to Integrate with Shopify Help Center article on how to integrate and connect your Shopify account with Klaviyo.
I hope this helps!
David