RAID5 is risky on drives that large, there’s a decent chance of a read error during a rebuild.

RAID6 will provide more protection but you lose two drives worth of capacity to the parity data. I’m not sure if a three drive RAID6 is actually possible but a three way mirror would be more sensible as you’ll avoid the extra computation of parity calculation.

Imo RAID6 starts to make sense in an array of 5 or more drives.