How can I show the selected variant on the live preview?

If your product consists of multiple variants that all have the same product image expect maybe a different color, then it can make sense to update the live preview with the current selected variant image.

In the live preview config, on the product layer:

Enable the setting shown in the image above. 

Image position

Leave this setting empty.  This setting is only required if you want to show the live preview on a specific image of your product.

Image gallery

The app will show the live preview on the main image on the image gallery of your theme. 

If you have set up the app to show the selected variant image, it is recommended to increase the preview size to completely overlay the image gallery of your theme.

Alternatively, you can setup the image gallery from the app: How can I setup a gallery with multiple live views?