(Divi): How to make WordPress load images of specific size for Blurb modules on given page with a funciton?

Elegant Themes (Divi) recommend a maximum width of 550px for blurb images (https://www.elegantthemes.com/blog/divi-resources/the-ultimate-guide-to-using-images-within-divi). So you should be resizing your images according to those guidelines for the images that you know will be used in your blurbs. This will ensure that your images don’t cause WordPress too much memory effort to resize them on the fly, and should also mean your images will have a smaller filesize too.