Just to register that since upgrading to the 3rd iteration of version 3 of Denoise the performance on my MacBook Pro has slowed measurably over the second iteration. Have switched GPU on and off in settings but still substantially slower.
Application & Version: Topaz DeNoise AI Version 3.0.3
Operating System: macOS 10.16
Graphics Hardware: AMD Radeon Pro 560X OpenGL Engine
OpenGL Driver: 4.1 ATI-4.4.17
CPU RAM: 32768 MB
Video RAM: 2047 MB
Preview Limit: 4492 Pixels