It comes down to how much you value you time, data, and how fail-safe the backups are. Nothing wrong with even striping the drives in a NAS as long as you know that the backups are good, the data easily replaced, etc. Conversely, the longer it will take you to come back from a failure, the more you value your time, the more precious the fidelity of the data, the more you should consider Z2 or even Z3 arrays. Not because failure is likely (hard drives for the most part are amazingly reliable) but because the recovery from a drive failure is less likely to lead to pool loss.
Enabling SMART helps, as do scrubs, to help highlight drives before they conk out completely. But as others here have discovered (
see this recent thread re: PSU failure leading to pool loss), pools may get killed by random events no matter what you do. Every step towards making the pool more resilient will improve your odds (mirrored SLOGs, mirrored boot devices, dual-redundant power supply (PS), dedicated uninterruptible power supply for each PS, etc.) but ultimately there are parts that cannot be easily made redundant in a home setting, such as the motherboard itself.
There are plenty of great resources out there dedicated to explaining the benefits and drawbacks to various pool configurations. Learn then settle on a pool layout that allows your pool to function for you. Don't be afraid either to re-configure stuff later on. If the backups are good (and I'd suggest having multiple sets), then there is minimal risk in nuking and rebuilding pools from the ground up. I did this with my latest pool, enabling the use of a mirrored SLOG by eliminating one of the spinning hard drives.
I'd have a look at this board also as an alternative to the C3xxx series:
The Supermicro X10SDV-2C-7TP4F. It features two PCIe 3.0 x8 expansion ports, two gigabit ports, a IPMI management port, two 10GBe SFP+ ports, a on-board LSI 16-Channel SAS controller, a PCI 3.0 x4 port for m.2, a 2-core/4-thread Xeon D 1508 (25W TDP), two SATADOM connectors, etc. and all that in a flex ATX board for about $500. Check the thing out, it's a pretty amazing solution for a SOHO build where you don't have to support a lot of users at once.
IMO this board is a better value than the C3xxx series because you get the benefit of a fairly future-proof assembly for the same or less money than the C3xxx offerings out there. There are more powerful Xeon-D versions out there that will need more Watts and which will also cost more. But the price overlap between the Xeon D series and the C3xxx series is somewhat baffling. As best as I can tell, the main benefit speaking in favor of C3xxx is lower idle power consumption.