A full X-Plane 12 installation with all scenery areas eats up over 93GB of SSD space. 60GB of that is taken up by global scenery, divided up into less than 20 distinct areas. In the past, there were only a few larger scenery areas, but recently Laminar Research has divided many of these areas into smaller selectable areas to help you only install what areas you need.
You can also install a large area of scenery and then remove individual tiles at will. TRhat way you can wind up with just the scenery you need. All other areas where you have not downloaded global scenery will just display a lot of water as if there had been a huge flood.