FYI, if you have a nVIDIA GPU, and I believe you have a MSI GeForce GTX 1070 Ti Gaming 8 GB, using Task Manager doesn’t display accurate figures. For nVIDIA there is a app called nvidia -smi which will produce correct statistics.
I also use MSI Afterburner and I just ran Afterburner with the main window minimized/maximized, but no difference. I wonder if it is to do with the display because I have an integrated GPU that drives the display?
Yes, the 2070 drives the display. Please be aware that I am NOT courious about the graphics card load. I am confused about the (8700K) CPU load at the same time. When the application is minimized the load is half of what it is when the application window is on the screen.