If the RAID LED is blinking and the two HDD "Access" LEDs are blinking in white showing that "RAID Rebuild" is in progress, can I switch off the RAID System and then turn it on later to continue the "RAID Rebuild"? Will this affect the integrity of the data stored?

This action will only interrupt the "RAID Rebuild" at that present time. However, next time when you turn the RAID System, the process will continue and should not affect the quality of the data stored.