Upon compressing images Rawsie generates and attaches either medium-size or full-size previews to your output files in order for you to be able to preview files in Finder and other apps.
You can select the size of previews after importing files by clicking a button next to "Generate previews" located under the list of image previews:
Should you choose medium or full-size previews?
If you are using third-party culling or automated editing software that rely on working with image previews, we would recommend selecting full-size previews.
For example, if you are using Narrative Select or Photo Mechanic to cull your images or ImagenAI to process them, we'd recommend using full-size previews, but you can as well try to compress a couple of images with mid-size previews and test if it also works for you. Unfortunately, compressing files with full-size previews generated comes at a price of a slower compression in Rawsie as we need to generate highly details previews.
If you are using just Lightroom, you can safely select medium-size previews as your best option. This is because Lightroom will anyway generate their own full-size previews upon importing files into it. Compressing with medium-sized previews is generally twice as fast as with full-size previews.