I can easily use Dropbox to browse photos that I've stored in the cloud. As soon as I tap on any item in a given list of images, Dropbox automatically generates a low-resolution version of that photo and serves it up to me in a preview window that is located right next to the list of images. Dropbox probably automatically starts generating previews in the background for whatever image folder I'm currently viewing, because I can quickly browse my entire photo collection just by swiping left or right in that preview window.

The web interface (but not the Apple mobile or desktop interfaces) to Proton Drive does offer a right-click option to generate a low-res preview. But this is one file at a time; I have to right-click the next file and select the preview option for that one to move from one photo preview to the next. This makes Drive virtually useless as an online photo album viewer and has already led my wife to decide to keep her Dropbox subscription rather than migrate her photo albums to my Proton Duo subscription.