If you won't be storing a lot of data (photos, video, etc.) then you don't need this. I always need it. This is something you can add easily later, though, if you decide you want it.
I suggested the Ryzen 7 3800 series because it's newer, but the 3700X would be fine. Ryzen 5 vs 7 is because there are more processing cores with the 7, and thus a significant performance gain over the 5. It's a way to future-proof a bit, IMO. I'm watching for components right now for a build of my own, and I will be buying the Ryzen 7.