Forcing my Mac to sync my Photos with iCloud - MacOS 11.1

Recent changes made in Photos on my wife's MacBook Pro (Retina, 15" 2013) don't show up on iCloud, such as: new albums and photos added from other sources (besides my iPhone or iPad).

A few days ago, I was trying to find a way to delete files on her computer so I would have sufficient space to install MacOS 11.1 on her computer. She was still using MacOS 10. She had no idea whether her files were being automatically synced with iCloud at the time. While poking around her computer, I found that her Mac was syncing with every App (including Photos) but not syncing with iCloud Drive, so I turned that feature on. Long story short, I was able to delete enough unnecessary stuff from her drive so she could upgrade to MacOS 11.1. Which was completed successfully.

Today however, we noticed that photos and albums (in the Photos App on her Mac) had not been transferred to Photos on iCloud. We're talking about some 3,000 items.

I've looked on the forum and used my search engine to find solutions, but they seem to be very old. Like 2014 or 2015 vintage. They suggest that if I shut-off my iCloud Drive on my Mac (System Pref>Apple ID>and remove the checkmark from iCloud Drive) then wait a 15 - 20 minutes before switching it back on, the iCloud Drive will somehow reset and start working properly again. When I attempt to shut off this feature, I get this pop-up:

What should I select at this point?

If I select "Remove from Mac", then I'm led to believe that ONLY the files on iDrive will be erased from my Mac. Articles suggest that if I select this option, then when iCloud Drive is turned back on, it will load all these files back onto my Mac which could be a long process. But, what about all the photos on my Mac that never sync'd to iCloud in the first place? Will they now sync?

If I select "Keep a Copy," where would it be kept? Note: I may have already done this when I was getting iCloud Drive set-up previously, and these "kept" files may be skewing my numbers adding to my confusion. If I already chose this option, how could I find and delete these "kept" files.

How should I proceed to:

1) Get my Mac and Photos synced with iCloud?

2) Find and Remove Photos I may have "kept?"