A lot depends on what you want to do.
It's important to remember than only originals count against the allowance. So if you sync photos from Classic, those don't count because they are smart previews but do allow you to do rough edits and add captions/titles/ratings/flags on an iPad or phone. But let's say you use LrMobile to take pictures or import photos/videos from the phone, or imagine using a flash card adapter to import raw files from your camera - these are originals and do count. Once you see them in Classic, the originals are safely on your hard drive and you can unsync them which frees up your cloud space allocation. This doesn't work for everyone, and I am always hearing of people travelling with just their iPad, then finding out they need more space, but in most cases it's possible to work with very little cloud space.