One Photo Viewer can be started from command prompt or batch script (.bat). All key value pairs in config file (F2) can be set as arguments. Note that these examples set block_config_save to true, so changes cant be made in that session.
Example: Start a slideshow of images in the folder (and subfolders) the .bat script is placed in. OPV will be started in full screen and always on top, also Esc press will exit OPV. Edit as you like, for example slidetime and slidezoom values. Rename by removing .txt or download .bat file directly (Windows don't like that).
It is also posible to start a macro by adding argument macro folowed by path to the macro, example: macro "C:\Users\you\Dokument\One Photo Viewer\macro\marco.opvm"