Compare JPG quality with one product photo first
Use a representative image to choose a sensible export setting, without assuming that a percentage guarantees a file size.
Pick a representative detail
Choose one working photo with the kinds of details that matter in your collection, such as a label, fabric texture, or a product edge. Keep the original. A sample chosen only because it looks simple may hide problems that become obvious in another image.
Use the same dimensions and resize mode for each comparison. If you change the crop or size at the same time as quality, it becomes harder to identify why the output looks different. Write down the setting you intend to reuse.
Inspect the actual downloaded copies
Export a JPG at a higher quality setting, then make another copy at a lower setting. Open both downloaded files at the intended viewing size. Compare fine text, sharp boundaries, and smooth backgrounds rather than judging only the preview thumbnail.
Check the resulting file sizes individually. The quality percentage is an encoder setting, not a guarantee of a particular number of kilobytes. The slider affects JPG and WebP; it does not control PNG quality. A JPG copy also fills transparent areas with white.
Keep a useful final working copy
Choose the version that meets your actual destination needs after reviewing it. Avoid repeatedly editing and re-exporting the already converted copy when you can return to the original. Use different output names so that comparisons do not overwrite one another.
Single-image processing is free. A pass unlocks multi-image processing and ZIP downloads within the documented limits. Inspect several different product photos before using one setting for a full collection; the result depends on the source content as well as the selected options.