It would be better to change the default "width" attribute for a data-width one to define the default size of the image. It's a bad practict to use width and height attributes on images. (if you scan your website on dareboost, it will be reported as a problem).
Even better option, let user configure the attribute they want in backoffice. You already allow to add a class, etc... for lazyload integration. Would be cool to be able to change that "width" attribute.
Thanks for your feedback. The ResponsiveImages plugin currently does not set a width or height attribute. All it does is to generate resized image copies and add a sizes attribute to your image tag. If there is a width attribute on your image it was there before the plugin did it's work.
Maybe another plugin or the wysiwyg editor has added it?