If the system-level backup is done outside the backup transaction, the IQ store backup will not be consistent with the IQ backup file.
However, a non-virtual IQ incremental backup together with the Virtual full backup will represent a consistent database. This is because the IQ incremental backup will copy all IQ store data and metadata that have changed during or since the Virtual full backup. Note that even the automatic commit and checkpoint that are part of the backup command modify the IQ store, making an independent system-level backup inconsistent. Trying to use the database without applying the incremental restore will give unpredictable results.