Hello RD,
Thanks for reaching to us.
It is due to different heights of images. In order to have same size image, I kindly recommend you preparing images you want before uploading them to your media library using the graphic editor (Photoshop or any other) to have a nice-looking grid or You need to find a third party plugin to achieve more functionality that best suits you.
For the Product Archive page, please navigate to Theme Settings > Product archives -> Products styles, here you can enable the Even product grid for desktop
option to align products if they have different height components.
https://prnt.sc/ASt5z0mmasuz
Please note that this option helps product items to be even, not resizing images, please see screenshot for better understanding https://prnt.sc/g2V_htGMgP5H
Best Regards,