When I press preview, then I see GPU performance in task manager goes up to 80-90% but when I render scene my CPU goes to 100% but GPU goes only upto 10-30%, not more than that. Is something wrong in my export settings ? In hardware setting I have selected both GPU and CPU.
My GPU is 1070 8gb and CPU is i7 8th gen,

And Iray is not working with the latest Nvidia Driver (418.81). It always shows Out of memory.
I wasted my two days making it work, then rolled back the driver to 417.71, it started working again.