I understand that 'Fast Mode' renders only 100 passes and in 'Accurate Mode', you can pick the number of passes.
However, in 'Fast Mode', Visualize does not give you any options to pick the render device, i.e. CPU, GPU or Hybrid, while 'Accurate Mode' allows for the same.
My main concern is, when in 'Fast Mode', is the software making use of the GPU as well as the CPU or is it only the CPU that is used for rendering? If the former, how is it different from 'Accurate Mode' set to 100 passes, because I seem to get better renders in 'Fast Mode' than in 'Accurate Mode' set to 100 passes.
Any details on how exactly this works would be greatly appreciated.