I would create a qtree in each volume, then create a default quota...identical to a setup in a non-vfiler, but use /etc/quotas in the vfiler root then quota on from the vfiler. In the vfiler root volume, create the quotas file, then from the vfiler context "quota on volname" or "vfiler run vfiler1 quota on volname". This will prevent users from writing over the quota but they will see the full size of the volume.
* user@/vol/staffusers 2G - 2G # 2G max, no file count limit, threshold at 2GB, but in reality probably make less than 2GB
* user@/vol/staffnores 10G - 10G