Screen grab improvement

I get almost no improvement when working with screen grabs (iMac Display Type: Built-In Retina LCD
Resolution: Retina 4.5K (4480 x 2520)`
I have before and after samples I can send as demos.
topaz-standard-4x gives the best result; my standard go-to of low resolution which works wonders on web image downloads is impossible, covering the image with grid-looking artifacts.


(Yes I found the iMac processor option that speeds things up but can introduce such artifacts, and turned it off.)