We do not use the SMVI for restores, only to take snapshots. For us, we only had to give the SMVI user
Datastore \
Browse Datastore
Virtual Machine \
Configuration \
Disk lease
Provisioning \
Allow read-only disk access
Allow virtual machine download
State \
Create snapshot
remove snapshot
This is the default VCB user permissions with the addition of the Browse Datastore permission, which SMVI requires.