Why 200 KB comes up
200 KB is a practical size for a blog photo or a product image that should stay sharper than a 100 KB export.
What happens to quality
You usually keep more edge detail than at 100 KB, especially after a sensible resize. It is still lossy for JPG and WebP, so text inside a photo can soften.
Why some images cannot reach 200 KB without resizing
A huge camera original may still need its dimensions reduced to land at 200 KB. A lossless PNG of a screenshot often will not. Switch that file to WebP if the destination allows it.
WebP is the default output on this page because it is often smaller than JPG and much smaller than a lossless PNG. You can switch the format if the destination requires JPG.