Moving photos to a new Mac from an old one - issues with permissions and iCloud
I suggest that you use the export function of photos. 


from the photos app

.. be sure you click on the photos tab

.. command+a to highlight all photos 

.. click on file  

.. click on export 

.. export ...  [ you can pick either of the first two.  I don't know what you might want. If you have made photo edits in photos, you want the first one. ]





if you did't export the photos to an external drive, copy the photos to an external drive.
use the import function on the other machine. 


My view, in short, is that placing you photos in iCloud is a method for loosing them. I recommend you get your photos out of the Apple ecosystem and store them as one photo per file on multiple external storage devices. For long term storage, don't rely on usb memory sticks nor external ssd drives.  LoC does not have data on the reliability of usb memory sticks.  Apple seems to be saying do not store photos on external ssd drives.  One device should be off site.  Using a cloud service is fine.  Remember a lot of cloud services are sync services.  That is should the file be deleted on the local device, the photo will be deleted in the cloud.  For this reason,  I never install the cloud service software on my computer.  I use only file upload.  For those who complain, my assessment is that the apple Eco-system doesn't match Library of Congress's requirements for digital archiving.

informative video:
http://www.digitalpreservation.gov/multimedia/videos/personalarchiving-photos.html

printed version
http://www.digitalpreservation.gov/personalarchiving/photos.html

General information on digital preservation:
http://www.digitalpreservation.gov/personalarchiving/