I want to set the image that appears here to be 1200 x 630 in size.

Hi there,

Instead of forcing the size, you can upload the image with its exact dimensions. The image is used in the GP Dynamic Image block, so it will display the original dimensions of the image.

Hi there,

yes you can force ALL the images to have the same aspect ratio.
For example this CSS will do that:

body:not(.single) .dynamic-content-template  img {
    aspect-ratio: 1.9 / 1;
    object-fit: cover;
}

But there are issues:

i) the browser may not choose the best sized image which will effect performance
ii) your first image will be badly cropped.

The simplest and best solution is for you to crop the image to the correct size before uploading.

You’re welcome