You can install Smartware Pro (that comes with the MCM) on up to 3 computers. But it’s just backup software, you don’t need it to actually access the MCM at all. Many people don’t install it at all, as it’s not the best software in the world. There are other WD apps for accessing the MCM from anywhere (the Cloud part of the MCM) if you enable it. Those are separate and freely available from the WD website and you can install them on whatever you like (for devices with suitable apps available of course).
As to your other question, the MCM 4TB contains 2x 2TB drives, as you say in a RAID1 array. So basically the MCM will appear as a single 2TB drive on your network, but everthing that you write to it will be written in duplicate onto both of the drives. So if one drive fails, you still have all of the data on the second drive. You can’t access the drives separately in a RAID1 array, but it gives the data redundancy and some safety (although of course it doesn’t protect against physical damage or theft which would affect both drives, nor the whole MCM going bad on you and corrupting everything).
What you can do is change from RAID1 to JBOD (“just a bunch of disks”) mode, which is how I run my MCM (also a 4TB). Then you basically just have two disks which can be written to completely independently, but there is no automatic duplication of the data (although there’s nothing to stop you writing it manually to both disks in parallel of course). On mine I have disk 1 as the target for backups from my networked machines (via Smartware), with disk 2 holding media for serving on my network to the PCs and Raspberry Pi on my network (the Pi runs Kodi and feeds the TV). The media is backed up on a 5TB elements USB disk which is plugged into the MCM, but that’s done manually (if I rip a DVD I copy it to both disk 2 and the elements drive).
But if all you want to do is have a networked 2TB storage space which is safe against a single disk failure, then yes RAID1 is the way to go.
I use Genie timeline pro (2014) (GTP4) and think I may be able to configure GTP4 to backup automatically.
Or more likely use RAID1, with my 1.5 WD external connected to the usb on the back of the MCM, with GTP4, taking data from drive 1 and backing up to external WD also, along with the 2nd MCM 2 tb drive as mirror.
