BCC Chroma Key Studio and GPUs

Just very short:
Using Vegas Pro 16. When rendering to Main Concept m2t my PC (intel 8700 16 GB, Nvidia 1060 3 GB) can sustain a 100% CPU usage and 15% GPU usage.
If I add BCC Chroma Key Quick in just 1 track the rendering CPU usage goes to some 55% and GPU to 15%.
I would have hoped for a much higher CPU (and GPU) usage - so what could be the Bottleneck here?
There is only 1 GPU (the 1050) on the machine.

There are many other potential bottlenecks that don’t show up when simply monitoring CPU or GPU usage. For example the time it takes to swap images from the GPU back to the CPU memory and then back to the GPU again can be a significant factor in some effects and it won’t show up in those top level usage statistics. Similarly CPU memory throughput can sometimes be a bottleneck. The real question is whether Chroma Key Studio is rendering as quickly as you would expect. It should be a fairly fast filter, but it can vary a lot depending on what options you have turned on in the filter. Some of the optional param groups in Chroma Key Studio and increase the render complexity significantly.