Piracy: ꜱᴀɪʟ ᴛʜᴇ ʜɪɢʜ ꜱᴇᴀꜱ

The general datahoarder hive mind seems to be moving away from shucking and towards manufacturer refurbished drives, see https://serverpartdeals.com/ for example, especially in RAID where you can lose a drive with impunity and warranty is uncomplicated by shucking.

In RAID and similar strategies the redundancy comes from a parity drive, which protects against the loss of one (or more with some schemes) drive, so if you only have two drives of the same size it's just a mirror (50% of total pool) but you can have a drive die without data loss. With four drives you get to use three of the drives (75%), five you can use four (80%) etc. Classical RAID uses identical sized disks but there are other approaches that allow different sizes e.g. mergerfs + SnapRAID or Unraid, here you lose your largest disk to parity.

RAID is generally faster than the individual drives, e.g. mirroring is nearly twice as fast.

Perhaps go with another 2*8Tb which will get you 24Tb usable and use the 16Tb for offline, preferably offsite backup (remember RAID is not a backup, it protects you from disk failure, but not user error for example accidentally deleting things)