RAID with three disks (RAID 5 vs RAID 1E)

The answer hasn't been RAID 5 for at least a decade, it's as dead as punch-tape - use 4 disks and RAID 10 it.

You should carefully consider whether RAID 5 will work for you especially in a RAID rebuild situation. The amount of reads required to rebuild a RAID 5 array is significant and can fall foul of an Unrecoverable Read Error (URE) which will cause you to loose the array and have to recover the data from backups. For example typical 8TB drives have 1 URE per 10^14 bits read so for your array there is a significant chance (~85%*) that you will not complete the rebuild.

Do you and your data a favor, use RAID 10 and a hot swapable disk system. Keep a spare disk to hand.

^*Yes that's a fairly naive view and you may get lucky but ... Did he fire six shots or only five?