Hi @Crunchii It is complex topic that can take some time to learn but if you want just understand basics there it many resources. As Image optimisation is not related directly only to WF the best thing you can do will be to find articles about this topic using any browser search engine. Here is one example.
and another one
Once you have decide what basic size you need, after image upload will WF do the rest and create images with sizes for other viewports.
If you will have time to learn more there is a new book you can purchase. It cover lots from this problematic and it can be challenging to read 500+ pages but…