After exporting the image files from macOS Photos App, you can access those exported files in ACDSee for Mac.
The steps are :
- Select the image files in the Photos App
- Click File | Export
- Choose one of the Export Options, e.g "Export # of Photos.. "
- Select the folder to which you will export
- Launch ACDSee. In the Manage mode, navigate to that folder you selected in the previous step