RAW files require a separate sidecar file in order to retain post processing edits. In Lightroom or anything Adobe based, that sidecar file is called an XMP. In DxO Optics Pro, the sidecar file is called a DOP. In Aperture and Photos app, it's stored in the main library file/database/folder. When you import a CR2 RAW file from your Canon camera into an iPad, you are seeing the JPG preview built into the RAW file and when you edit from the iPad, you edit the JPG inside of that RAW file. When you save the edit, it will make a JPG that is separate from your CR2 file. When this synchronizes over iCloud Photos to your Mac, the main RAW file is still there but no edits take place on your RAW. You have to save the edits to another JPG before you can see what you did post process in the Photos App on your iOS device. This means that while you get the RAW in the Photos app on your Mac, you also get the JPG you did the edit on. You have to press on Duplicate and Edit to get that separate JPG. Inside of Photos App, you can only recover dynamic range so much as well as control noise. Either way, you are creating a JPG from the JPG preview in the RAW and that JPG is processed by Apple's RAW so that it gets a specific view of that photo before you even start post processing on it.