I agree with Joseph’s approach.  When I started my conversion process, most of my 50K+ photos were scanned from negatives, slides and prints.  Once I had all photos in folders by year (sometimes just approximate years), and then within albums of specific events (vacations, holidays, trips, etc) I selected each event and changed the YMD/time of the photos, generally in blocks.  It didn’t have to be an exact date/time, just enough to keep the events sequential.  I also adjusted the location of all photos in a block.  Generally, I didn’t worry about the exact location.  If it was a vacation on Maui, I just dropped them all on a pin in the center of the island.  I also created a folder for each year called “yyyy-01-01 | Misc”  that I stuck miscellaneous photos that could not be easily classified by event.  After that project was over, I started the face recognition process and occasionally go in and verify new phots as the face recognition process does it’s magic.  

I now have over 73K photos in Apple Photos, all of the most recent 20K+ taken from my iPhone which automates everything.  Generally speaking, when talking with friends and relatives, and old times get brought up… I can find a specific photo within a minute or two by the combination of location, date (usually year), and face recognition. 

I still create albums of my events occasionally, generally just a few time a year, when I sync my photos with with those from my wife’s iCloud account.  However, these chronological albums are not quite as important as they once were (especially during the process above).   Apple does a great job automatically creating moments using dates, locations, people, etc.   Generally those are good enough.   Still, I go go through Joseph’s classification system because it is fun to do.