I hacked a little tool / plugin together to find out how fast premiere could actually render frames without anything interfering. This is tool is as small as possible and just renders video frames and throws them away again. No file output, no export, no nothing. It tests the premiere part only!
In the end you'll get a little popup telling you the theoretical max. frames per second that premiere is able to deliver for the loaded project / sequence:
(Considering that I am getting like 430 fps with nvenc h264 this is really not bad!)
Discuss the tool and your results here: Vouk's Render Performance Test
With this tool you can also find out if h264 hardware (iGPU) or software decoding is faster on your system. Or is it faster to use the mercury engine, or not? Feel free to test and share your results on twitter.
Please note I am "abusing" the error message functionality at this point to display the results. There is no rendering error. It is just a handy mechanism to display the results right now.