If you want it for 'regular use / TinyMCE etc', you typically use the 200px image and scale it down for mobile. You should do that with CSS, something like
img.myimage { max-width: 200px;}
@media only screen and (max-width: 600px) {
img.myimage {
max-width: 100px;
// or width:100px;
}
}
Note: srcset is better if possible, since it only sends the smaller image to the browser (phone)
Add picture method to to ImageScaling and include it in @@image-test. Picture tags only work on Plone 6, with several other branches for picture variants merged. See plip-image-srcsets.cfg. If not available (like on Plone 5.2), an ordinary image tag is created. [MrTango] (#113)