Davinci Resolve with fast CPU but Slow GPU
From what I've read, Resolve very much depends on your GPU power -- speed and VRAM. I believe there's a preference to turn off at least some GPU usage, but that's probably more of a workaround for something crashing rather than something to be done on a normal basis.
Probably the best place to ask would be the Black Magic forums and over there, Carsten Sellberg answered a similar question with:

In Resolve the CPU is used to run the app, disk I/O and compression and decompression of codecs.
Resolve does all its image processing in the GPU on the graphics card. More CUDA/OpenCL Cores are better.
There are two factors that is important for the Graphics card. The first is, that it have enough vRam to hold a single video frame. For 4K is the absolute min 6 GB of vRam, but min 8 GB of vRam or more are recommended.
The other factor is the CUDA/OpenCL performance. Higher CUDA/OpenCL performance gives a faster Resolve.