Hi! A GP Pro member here with a bug report for WP Show Posts. I hope it’s ok.
I was over the moon a month ago when I finally figured out how to use smaller image files with WP Show Posts. I used the following solution provided by Tom: https://generatepress.com/forums/topic/image-sizing-not-working-with-amazon-web-services-and-wp-offload-media/.
The code I use is:
add_filter( 'wpsp_default_image_size', function() {
return 'medium';
} );
Now I noticed that the filter works only for desktop. When the page is loaded on mobile or tablet, full sized images are loaded.
I noticed this first in Firefox Inspector and can see the same if I run webpagetest.org with both desktop and mobile emulation.
Thanks,
-Rauno.