Hi there,
if you DO NOT select a Media Attachment size in Customizer > Layout > Blog –> Featured Images then the WordPress SRC-SET images will remain intact, and the browser will load the most appropriate sized image for the different screen sizes.
If need be you can change the Media Attachment sizes WordPress settings or include other size that are best suited to your layout:
https://docs.generatepress.com/article/adding-image-sizes/
Please note that Retina/HD screen devices will generally look to use a x2 image size.