[NAME] Rubin My response in this post may answer some of your questions. "Can I image or clone the entire SSD or do I have to do this for each partition?" I would use Macrium Reflect Free Edition to image each partition, the reason is that since the new SSD is larger you will what to resize the C partition when it is restored to the new SSD. I would restore the partitions in the same order as on the old SSD. "Then, to copy over the old SSD contents to the new one, do I have to use a PCIE adaptor and place the new SSD in it for copying?  Alternatively, am I to create a bootable USB stick or DVD and copy from it after booting from it?" You don't need an M.2 to USB adapter or a PCIe adapter, you just remove your old SSD and install your new SSD. With the imaged partitions of the old SSD on your HDD, you boot the Rescue Media you created in Macrium Reflect to restore the images from the HDD to the new SSD. 
There are lots of threads in this forum about changing out the Toshiba nvme SSD that came with the XPS8930, but lots of permutations and variables, so I want to make sure I have this straight before I start playing around with my computer. I have a 256gb Toshiba nvme SSD and a 1tb HDD.  I am running out of space on the SSD and want to get a 1tb nvme SSD to replace it.  (I know that some of the better SSD's want their own drivers run on AHCI rather than RAID and I already have switched my system to AHCI, so that much is ready to go.)  I have migrated from HDD's to SDD's before, using software supplied by Samsung, but haven't tried going from an SSD to another SSD and it doesn't look quite as transparent, at least based on what I have read here. I know that I can create an iso with Macrium Reflect that is a copy of the existing SSD, but how do I actually get that on to the new SSD after I replace the old one?  Do I image the SSD or clone it?  Can I image or clone the entire SSD or do I have to do this for each partition?  Then, to copy over the old SSD contents to the new one, do I have to use a PCIE adaptor and place the new SSD in it for copying?  Alternatively, am I to create a bootable USB stick or DVD and copy from it after booting from it? I gather that I also can buy an external USB case for the drive and copy to that, but, since those cost at least $40 or so, I would prefer not to invest that much in something that I probably will use just once. I'd appreciate any guidance you good folks might be able to provide!  Thanks. 
XPS 8930, I just want to upgrade my NVMe SSD