A hero image often appears beside or behind the main heading. Check where the subject, text and controls sit at different widths before choosing an export. A face near the edge of a desktop panorama may disappear in a tall phone crop. A larger file will not fix that framing problem. Make a separate composition when the layout needs one, using your design or photo editor.
This tool can fit or crop a supplied photograph, but it cannot extend the background, remove objects or create empty space for copy. Do not rely on sharpening to make a busy background suitable for text. The website still needs adequate contrast and a layout that keeps the message readable. Keep the source master so you can create a different phone crop without repeatedly editing the already compressed desktop delivery file.