Rendering and GPU utilization: Fusion v. Resolve

Curiosity question.

I mainly am working in Fusion 9.02 standalone (free) and jump into Resolve (free) only as needed for editing and final renders.

I have a 3 year old AMD W7100 video card, which was marketed as a workstation card. Both Resolve and Fusion are set to utilize OpenCL.

When rendering in Fusion, the CPU is fully loaded, but the CPU never gets above 5% utilization. This is without any particular FX, just some simple video and 3D model integration, and occasional motion blur.

But when rendering in Resolve (either transcoding or rendering after editing), the GPU utilization jumps to 40% or more, and the CPU is at a comparable level. Once again, this is without any FX.

Is it possible that i have some setting in Fusion that needs to be tweaked to improve rendering, or does Fusion and Resolve basically use two different render programs?

In fusion only some nodes uses the OpenCL code, most of the time it's CPU