What happens if I add 175GB of photos & videos to my iCloud Photo Library via the Photos for Mac app on my iMac, but my iPhone only has 32GB of total space? I've enabled "Optimize iPhone Storage" on my phone, but let's assume that I've got about 20GB of other stuff (apps, music, movies, documents and data, other) on my iPhone, leaving me only a couple GB to spare for all of the photos? Will it be smart enough to limit overall cache size and more or less force me to load images on-demand by pulling them from iCloud when I need to view one full-size? Please advise. Thanks!