You can use the transport argument to define how your options will be applied to the preview.
There are 3 choices available: refresh, auto and postMessage.
postMessage docs tooThis argument uses the
postMessage module. Please make sure you read the documentation for the postMessage modulerefresh
By default all fields use the refresh method. This will force-refresh the preview pane in the customizer when the value changes.
auto
If your field already contains an output argument you can set transport to auto. This will allow Kirki to auto-generate the js_vars argument according to your output and make the field work seamlessly both in the frontend and in the customizer without any code duplication.
postMessage
If you use the postMessage method, you can either write your own Javascript to change things in the preview area or use the js_vars argument. If you decide to write your own scripts – which is highly advisable – we advise you to first read this post on developer.wordpress.org as well as this blog post on Otto’s blog.