Need some setup advice on a TS-X73A

[Bp_968]

I have the 8 bay TS-X73A. I have 4 total 18TB drives going into the bay and plan on using RAID1 (in two pools/arrays) or RAID10, OR Raid10 on ZFS. I previously had a homebuilt server running Solaris and ZFS on 10 2TB drives using RAIDz2 (it was a monster) and 48GB of ECC RAM.

I'm stuck on a small handful of issues.
1) Can I run ZFS/Hero on the included 8GB of *non*-ECC ram included in the unit?
2) If I run RAID10 in standard QTS I will need a UPS I assume because if it loses power during a write it could be a serious issue (unlike how ZFS is fairly robustly protected from data issues due to power loss?).
3) If I run ZFS should I install the OS on an SSD (either in a spare bay, or in one of the M.2 slots?) Should I install the OS on a SSD regardless?
4) ZIL/L2ARC/etc: I did not have an SSD based ZIL or ARC/L2ARC setup on the old ZFS machine and never saw serious limitations (I would often hit 600MB/s in tests over 10gb infiniband). But that machine had 10 disks and 48GB of Ram.

I am specifically using the NAS as a general network backup solution to backup the C drives on the three PCs in the house, be a central file server, and likely provide some multimedia services (Plex, possibly audio streaming, and hopefully as a nvidia "instant replay" target so I can lose the USB HDD connected to my gaming PC).

I'll be storing the wifes business on it as well (she is a wedding photographer) and currently we do triple+ backups of those (2 cloud locations, and 1 or 2 local locations). The NAS will become the new primary local location for those files. They tend to grow at about 2-3TB per year so mirrors or RAID10 seems like the safest setup.

The NAS is connected via 2.5GbE and a 2.5GbE switch and will likely have 10GbE added at some later point once enough drive(s) have been added to notice the speed difference.

I do understand the only way to increase my raid size using ZFS is to start a new raid, meaning I would have to "grow" it at a minimum of 2 disks at a time (mirrors essentially) or outright rebuilding the whole pool.

My priorities are 3 fold: #1, data integrity and protection, #2 speed, #3 long term ease of use (so my wife can at least grasp the basics of keeping it running if I were not around to help her with it for example).

If I need to buy something else I can: some ECC SODIMMs, or a 500-1000GB M.2 SSD.

And one last question: If I install the OS on a 2.5" SSD right now, could I later shutdown the server and image the disk over to an M.2 SSD to free up that drive bay? Or once the OS is installed I'm "stuck" with it being on that disk/slot/location?

Thanks!!