Hi raskull,
I’m not totally sure but I think you can copy the /views/widget-admin.php file to your theme /image-widget/widget-admin.php and then you can update it to remove some fields.
Then you can filter the various filters to override things. You can see the filters in image-widget.php around line 90 – 104.
image_widget_image_width
image_widget_image_height
image_widget_image_link_target
image_widget_image_align
add_filter('image_widget_image_width', 'raskull_overide_image_widget_height');
function raskull_overide_image_widget_height() {
return 300;
}