Do uploads really process in the background, or do I have to wait around?

Really in the background. You can start a large upload, and while the files climb up, you can move on to other albums, edit settings, or go make tea — the processing continues without you babysitting it. The dashboard keeps you informed as storage use and photo counts tick upward. This matters more than it sounds: during wedding season you're often uploading one event while delivering another, and the ability to run those in parallel is a genuine workflow saver.