Index will be much harder to get. Preordering now, you won't see your VR setup until early October.
Rift S will be more readily available as well as half the price.
In addition to the Oculus Medium sculpting app, there is:
SculptVR
MasterpieceVR
Other popular artistic apps to check out in VR are:
Tilt Brush
Quill
SculptVR, MasterpieceVR, and Tilt Brush are also available on Steam, while Medium and Quill only on the Oculus store.