This is what Apple have to say about RAW on the Mac and iPad:
How Photos and iCloud Photo Library handle RAW images
Learn how to work with RAW images using iCloud Photo Library and Photos for macOS.
iCloud Photo Library keeps your photos and videos up to date on your iPhone, iPad, iPod touch, and Mac. If your photo library includes images in RAW format, you can view and edit them on your Mac.
About RAW files on your Mac
The availability of RAW files on your Mac depends on a few conditions:
If you have the Download Originals to this Mac option turned on in Photos (Photos > Preferences > iCloud > Download Originals to this Mac), then your RAW files are always present in Photos on your Mac.
If you have the Optimize Mac Storage option turned on, then your RAW files are stored in iCloud Photo Library. Photos saves disk space on your Mac by displaying optimized JPEG versions of your RAW images. If you edit an optimized image on your Mac, Photos downloads the RAW file for that image.
When Photos downloads a RAW image from iCloud Photo Library, it creates a new full-sized JPEG for optimal viewing on your Mac. It won't replace the RAW and embedded JPEG file already stored in iCloud. iOS devices will view the embedded JPEG.
RAW files that you store outside the Photos app library (for example, in your Pictures folder) are always present on your Mac, but aren't stored in iCloud and won't stay up to date in the Photos app on your iPhone, iPad, or iPod touch.
RAW files imported to iPad with the Camera Connection Kit
If you import RAW images to an iPad with the Camera Connection Kit, turn on Download Originals or edit the images on your Mac so that the files are available on your Mac in iCloud Photo Library.
When you work with RAW images on an iPad, the iPad shows the embedded JPEG thumbnail of the image created by the camera, not the actual RAW file.
Published Date: Jul 7, 2017
It looks like you’re seeing the lo res embedded jpeg for some images
.. Good things come to those who wait