Edit RAW photos as original s greyed out

And the option "Reprocess RAW" is only available, after a software update changed the RAW processing algorithm. Then you can decide, if you will keep the current version of your photo or reprocess it with the new, hopefully improved, RAW support.

As long as you are able to edit your photos, you do not need to worry about the two dimmed out options. They will only be active, if they apply to your photos. Photos will always use the RAW file to edit your photo, if you only import the RAW file and not a pair.

You're welcome. Importing only the RAW will save storage, and you will have the best quality for further edits. Only if you are using the smart presets of your camera as well, it might be worthwhile to save the JPEGs too (perhaps on an external volume), because Photos for Mac is discarding all camera effects when importing the RAW files. Keith Barkley's user tip for Aperture applies to Photos as well: The Big Three: Setting your camera for the Best Aperture RAW Results

Have you imported the files as raw/jpg pairs. (You shoot raw and jpg, and both files were in the same folder when imported). If you have you'll also have an R or J stacked image in the icon as shown below.

The use raw as original is only available if you have both raw and jpg version of the same image installed. It is not needed if you only have raw images.