i58600k

hi , normally i get 55,60 fps at ultra but when i use " resolution scale " at max , the cpu start to work at 30 % ,my GPU at 99 % and my fps drops to 20.....why ? this is normal ? any way to fix or force cpu ? i have an rtx 2070 + i5 8600 k + 24 ram ddr 5 i guess , i forget. SD HD and Win10. I...