According to the recommendations from Adobe, I'd get 16 GB RAM (I never ran Lightroom Classic with less, actually, even my mid 2012 15" MBPr has 16 GB, Adobe recommends 12 GB). Also, 256 GB SSD seems a bit small. Curiously, right now I'm pondering more or less the same thing as you, but I'd be getting 16 GB RAM and probably the 1 TB SDD. My biggest concern is the lack of a dedicated GPU.