Merging Photos libraries
I have overlapping photos libraries in 6 places. 1. an old iMac; 2. An external drive storing the Time Machine back ups for my old iMac; 3. My current iMac; 4. an external drive that has some but not all of the pictures and videos from the old and new iMacs and, my iPhone which is synched to the iCloud and the cloud which has some but not all of these photos. I also have just upgraded my iCloud storage plan to 2TBs to accommodate all these libraries residing in the cloud for at least a while.
What is the best way to merge these different libraries? Will the resulting merged library retain the places and names associated with the pictures? Will the resulting library resolve duplicate pictures?
At the end of this process I would like to have the Photos stored in the iCloud, and on an external drive with a sub set (perhaps most the recent or folders I am currently working with) stored on my new iMac. The old iMac is only used in the guest room and will not be using iCloud storage.
Lastly when should I cull out the many pictures that I do not need to saved. Should I do that before the merger or after I have merged the libraries?
I have avoided trying to consolidate all these various libraries because I anticipated it being a very long and tedious process. That may be the case, but understanding the best way to do this will get me started.
Thank you for helping me out with this.
Tiger 927
iMac 27″, macOS 10.13