Hi Tiago,
1. You can set the featured image to use your medium size with a filter:
add_filter( 'generate_page_header_default_size','generate_change_default_image_size' );
function generate_change_default_image_size()
{
return 'medium';
}
2. This is much harder, I need to dig into the code to make it possible to have different image sizes associated with different widths in masonry. Currently I don’t think it’s possible.
What I would do is use CSS to resize your images for now if this is needed. Each masonry grid size has a different class, so you can target the .post-image class:
.width6 .post-image {
max-width: 400px;
}
article:not(.width6) .post-image {
max-width: 200px;
}
Just as an example 🙂