Photos

The Photos application is a part of Mac OS X. It is not available on other systems. The Photos Library is package of files, a mixture of image files, working copies, relational databases. It is very difficult to find the edited versions inside, because they are not saved as image files. only the original image files are saved in the subfolder "Masters".

And Photos requires that you save the library on a volume with the file system format MacOS Extended (Journaled) or APFS. Your PC may not be able to read an external drive with this file system format.

If you want to access your photos from a different computer model. I would use the command "File > Export > Export unmodified Originals" to export all original image files from Your Photos Library to an external drive with a file system, that can be red by a Mac as well as a PC: I would use the subfolder preset "Moment Name" to save the photos in folders named by the location and the date. This will help you to find photos.