To start all the settings over again, delete
/config on the flash drive, but do NOT delete the .key file
To wipe out all of the hard drives,
From the command line,
rm -rf /mnt/user
Or alternatively with the array stopped, change each drive's filesystem from XFS to instead be BTRFS, start the array and it'll want to format the drives, do that they stop the array and change the disks back to be XFS and format them again.