GPU VRAM and other applications
Substance 3D Painter is not alone when working with the GPU, other applications can do the same. The Unreal Engine 4 for example will require something like 70% or even 80% of the GPU memory. A solution to ensure good performance while keeping theses applications is to be sure Substance 3D Painter is launched first in order to request its own VRAM allocation. Still, some software can require some parts of the VRAM dynamically and can still be in conflict with Substance 3D Painter even if it was launched after.