Heya,
It's a good drive. But basically most of the major driver makers pushing their consumer NAS level drivers have similar performance & life. Having the best drive in the world is not the answer to a back up. Think of it as just another place to hold things, one of several, and you're going to fare better long term.
I'm not sure there's enough overall data to show if a SSD vs HDD will keep data, unplugged in a safe, for 100 years, and remain functional when repowered after that time period with intact data. I'm kidding obviously (though that data doesn't exist!), but my point is, you probably will not need to worry about this. You will be replacing those HDD's every few years anyways. They are not life-time purchases nor solutions, so don't get one and let it sit hoping it will last longer. You should easily get a few years of constant use out of these drives, SSD or HDD. But don't expect 10+ years.
If the drive is connected to a windows machine and is present in the disk manager, it will be accessed. It will spin down based on power settings in the control panel, but there are tons of windows services that will crawl the drive. You'd have to turn them all off or disable them on that drive to prevent them from spinning it up or accessing it randomly. Even then, I promise you, Windows will still access that drive here and there. That said, I would not worry about this, the NAS drive was made to run 24/7, hot, for a long time. It's not made to just sit in your computer, in low power state, doing nothing, except once every 3 months. You didn't need to get a NAS drive to do that. And if you're worried about redundancy, simply use more physical drives instead of buying a single expensive drive hoping it won't fail (obviously you're not doing that, you have another backup, but you get the idea). If you want the drive to not be accessed, it needs to not be attached to the machine during the off-time. USB3.0 or eSATA is a way to access it when you want to, and keep it cool and asleep and in a safe, when you're not using it. If it's in your system, connected, I would never consider it an actual backup--more a working drive. Plugged in, it will always be subject to catastrophic power failure, fluctuation, physical damage, environmental damage, etc.
The drive will spin at it's maximum speed when it's asked to. Even then, that's just it's average sustained. Don't worry about this. Finding a way to set it to run at 1,000rpm's will not increase it's life span or durability. Enjoy the faster file transfers.
You can turn it off in BIOS, but it depends on what settings you're using for your ATA/Serial bus. You can totally make it "disabled" and then notice it shows up in Window's disk manager, simply without a drive letter attached, but it's powered and I bet you it got accessed a little here and there as it was being quivered and added. There's no real practical reason to disable these drives. Either take them out, or leave them in and use them.
There are all kinds of opinions on backups. I am of the mind that it's all about levels of protection, and the more levels you feel you need, the more separate locations you have to have to achieve it.
About HDD's, you really should be in the habit of changing them out every so often. Same reason the companies do the same thing. They are not forever. They fail. Always. Eventually. They fail. So you simply use them while they're good, and change them before they fail. Your backups are for when they fail before you reach that point, or in case other things happen. As you accumulate photos, your space required increases anyways. Plus, mass storage is stupid cheap. 4TB is like $120 these days for a good drive. Every 2 years or 3 years, you could get another one, with even more storage. That's super inexpensive if you think about it. $5 a month for that storage, if you put it in that perspective of 2 years.
Very best,
