Its hard to tell to whom the comments are addressed.
The 240Gb SSD is a boot, system, and applications drive and holds the operating system, so it will boot in about 10 seconds, closer to 6 with the NVMe version, some of your most used applications, including a big game or two, where cut-scenes and levels will load very much faster, and you working edit, scratch, and system files for faster programming. Your HDD is a storage and archive drive, where big, less often used files and games you are not currently playing go.
Yes, the case is compact, but what is a case for? It is a box to contain, protect and cool your parts. Have a look at these builds from school.
http://www.tomshardware.com/forum/id-2625445/build-log-consolidated-middle-school-builds.html All the cases are comparatively small, but plenty big enough.