If you move your head around, do the bright spots follow your eyes? ie, is the area centered in front of your eyes always the brightest? Could it just be a viewing angle thing since the screen is so large and you're so close?
Yes there is some darkening at the sides due to viewing angles which makes shadows more pronounced. If you look at the photo shadows are uneven therefore they cannot be solely attributed to viewing angle. Shadow also varies with brightness (it's harder to notice at 100% brightness) therefore I hope with 480Hz PWM update I will find a setting that suites me.
EDIT: after upgrading, there's less flicker. I think I can use down to 50% of brightness now. However shadows and dirty screen effect is still there. Btw, Anker Poweline+ USB 3 cable worked for me just fine (I read there are issues).