finding large videos in the OSX Photos app

1. Navigate to Pictures folder
2. Right click on Photos Librar and Show Package Contents
3. Open the originals folder (prior to macOS 10.15 / Catalina, the 'originals' folder was named 'Masters')
4. In search bar, type mov, then choose Type 'Movie'
5. Make sure 'Masters' is still the search target
6. Right click the column headings and tick 'Size'
7. Click Size column header to sort

Do not change anything in Finder. Just use it to identify the videos, then go back to Photos to make changes.

This can be done via the free version of PowerPhotos (brew cask install powerphotos)

1. Open your Photos library in PowerPhotos
2. In the menu bar View section, select As List and Show Columns → Size
3. Click the size column to sort by file size
4. You now have a list with where the biggest files are easy to spot