1. This might help: https://generatepress.com/forums/topic/page-and-post-headers/#post-125452
2. Adding 0 as a height or width will enable proportional resizing. You need to set a width to enable a hard crop.
Image Crop Position was removed as the script wasn’t using core WordPress functions, which I’m not a fan of. It may make a come back with some recent WP developments 🙂