I currently have a late 2013 27” iMac w/ a 3Tb fusion HD. I’m considering a 2017 27” w/ a 2 TD SSD, but I have about 1TB on my current machine. I work with 65MB Nikon NEF files and have a large and growing photo library. I was told early on that one should never exceed 50% of disk capacity when working with spinning HD due to speed, effificiency and fragmentation. Does the same rule hold true for SSDs? If I get the 2TB SSD, would I need to plan to off load my photo and possibly iTumes libraries to an external disk? I do not want to compress the images due to loss of data.