@nathan-delle I think it has to do with Wix’s dependency on absolute parameters…which leaves it kind of up to you to match the size of the element in the editor and the resolution of your rendered image.
One trick I’ve used in the past to get around this somewhat is to render the image as a png leaving some blank space around my image using Illustrator or Affinity Designer (any vector design program really). That way, if you set the image to anything but stretch inside the editor, you have more wiggle room to work with and don’t have to worry about cropping.