One of the reasons why you may not see 100% GPU utilisation even when your GPU is the bottleneck is that the GPU has to spend a considerable amount of time waiting for the CPU to tell it what to do, so it may only be busy 60% of the time, but still not be done rendering a frame before the screen needs it.
OS: Windows 10 64 bit Professional
CPU: AMD Ryzen 5900X
RAM: 16GB
GPU: Radeon Vega 56
CPU: AMD Ryzen 5900X
RAM: 16GB
GPU: Radeon Vega 56
