This is a great feature and I can’t wait to try it in the Linux client when it’s available!
I vote for retaining both paradigms. As an example, pCloud, which I also use, supports both the cached virtual drive and hard-synced folder paradigms. It allows the flexibility to have a core set of folders that you always want synced, while allowing lower priority or lesser-used stuff to come and go. For me, the example is my core document and development directories, which I always want fully synced, and then hundreds of GB of camera raw files, which I definitely don’t want burdening all of my systems and would want those to be on-demand and cached, so I don’t need to manually sync and unsync them, as they are distributed in a multi-level directory hierarchy comprising dozens of folders.