Best redundancy option for 4 bay ITX case?

I'm planning out a new TrueNAS ITX build with 4 bays. Historically I have always ran all 4 bays with RAID-Z1 (or RAID-5 on other systems), however I am more paranoid than I used to be. With HDD capacities as high as they are now, I would be fine using the extra bay for redundancy rather than capacity. Having only 4 bays leaves me with a lot of options:

• Mirror + Stripe
• RAID-Z2
• RAID-Z1 with hot spare (I assume this isn't a good option based on what I've read)
• RAID-Z1 with...

Best redundancy option for 4 bay ITX case?