Quick answer
In those cases, both file size and dimensions matter. A product image may need to stay visually clean while becoming light enough for fast loading. A CMS asset may need to stay under a platform limit while still matching the expected width and height.
Start with the platform's file-size limit, then decide whether to preserve dimensions or reduce width and height. Exact dimensions are useful when the platform specifies pixels as well as KB or MB.
What usually works best
This is useful for ecommerce teams, bloggers, marketers, and support teams who need a faster way to prepare images. Instead of exporting, reuploading, and retrying over and over, they can adjust size and dimensions in one place.
For product photos and CMS assets, change one variable at a time: set the required file-size target, check the result, and reduce dimensions only if quality alone cannot reach the limit.
If it still fails
For many users, the real problem is time. They need an image that uploads correctly, loads quickly, and still looks good. A size target plus dimension control usually gets them there faster than a generic optimizer.