Just wanted to share my experience with using Pro/customizer when the theme is Integrity/Dark.
When trying to add elements to columns, if text, the default is black text so you cannot see it to edit it unless you highlight it.
Simple fix: if the theme is dark, default text color should be white.
This is also a problem to see that the section or column is highlighted and ready to have something dropped on it. Dark theme obscures all of this.
I guess to do a wysiwyg customizing experience, we could change the theme to light while we customize and then change it back to dark to go live. This defeats the wysiwyg experience.