I'm not very tech savvy, but I'm imagining, a smaller program monitor means less pixels. By "small program monitor, i mean sides are dragged to make size small and not full screen, or docked on a small corner. Does that, if at all, reduce the load on your system?
PS - I know about the quality option 1/2, 1/4. Just wondering if reducing PM size helps. Thank you!
I should probably ask around to verify my answer because it's a good question.
My personal experience is that the least overhead for the Program Monitor for any NLE is when it is at 100% size and you also display it at 100%. Scaling the Program Monitor up or down takes more system resources. The problem is that it is impractical to display larger formats at 100%, so the compromise is usually scaling the Program Monitor down. I usually work in "Fit." Sometimes I scale down the Program Monitor to smaller than "Fit" for effects staging. Sometimes I scale them up if I need to see detail. Fit is the best compromise for working with HD and 4K formats. Our system requirements allow for any UI scaling, so as long as your system is up to the task, so is viewing your Program Monitor.
I don't think it makes much difference on the CPU or GPU but it can affect the image quality. If you enable high quality playback it will clean up the pixelation. That being said high quality playback will affect the performance.