Yes, it can handle very large photo and video libraries! Users have reported successfully backing up over 20k photos and videos without issues. I don't have 150k photos and videos for testing.

Currently, direct backup of photos and videos stored only in iCloud is not supported. I will consider adding iCloud integration in a future update.

The original album and photo information will be preserved. Photos and videos will be organized into backup folders by Device Model/Year/Month.