Can I use LR CC storage only for catalogs and smart previews?

Longtime Lightroom 6 user, just getting started with LR Classic and LR CC. I expect to use primarily Classice (400GB of images) and not ready to upgrade storage beyond my current 20GB.

Q: Can I use the LR CC cloud storage to backup my catalog and/or the smart previews folder?  Or would I have to use the full CC approach to access that storage?

Thanks,

Frank