how can I find and review individual photos in my Time Machine Backup of my Photos Library?

You will have to restore the Photos Library from the Time Machine backup to some folder, where you are not overwriting your current library. Then open the restored copy in Photos to find the photos you want to retrieve.

Photos cannot dopen a Photos Library directly as a part of a Time Machine backup. and since macOS 10.15 Catalina Photos is renaming the original image files in the Photos Library package, so we can no ,oger access them directly in the package and find them by the filename.

As a small addition to léonie's comment, when you restore a Photos Library, Time Machine will ask if you want to replace the one you have or keep both. If you choose "keep both," then it will save the restored version with a slightly modified name-- so you don't have to save to a different folder.