I much prefer to have separate partitions for System , programmes etc and another for data. I think it makes backing up so much quicker and easier. I have put all my data , including Outlook, in folders and sub folders of " My Documents" on my data partition, and use Freefilesynch or SynchToy to back them up with a mirror image daily - takes only a few minutes. I use ATI to make images weekly of the system partition. (Both on other drives). I do occasionally clone the whole drive to yet another back up.
Microsoft Lumia 950 vs Lumia 950 XL: What's the difference between Lumia 950 & 950 XL?