To completely overwrite _module.less of Orange_Checkout module in a custom theme, the developer should place the file in the Custom/theme/Orange_Checkout/web/css/source directory. This will override the default _module.less file from the Orange_Checkout module and apply the custom styles to the theme. The Custom/theme/Orange_Checkout/frontend/web/css/_module.less and Custom/theme/web/css/source/Orange_Checkout/_module.less paths are not valid and will not work, as they do not follow the theme structure or the module naming convention. References: [Theme structure], [Module naming convention]

To override the parent theme styles, the developer needs to change the web/css/source/_extend.less file in the child theme. This file is used to import and extend the parent theme styles without modifying the original files. The developer can use the @import directive to import the parent theme styles and then use the .lib-css() mixin to override the CSS properties. For example:

@import ‘source/_extend.less’; // Import parent theme styles .lib-css(color, red); // Override color property

The web/css/source/_extends.less and web/css/source/_theme.less files are not valid and will not work, as they do not follow the theme structure or the naming convention. References: [Theme inheritance], [Extend parent theme styles]