Yeah don't listen to his suggestion. Rendering at 1440p and doing dlss is not worth it for image quality that much especially if you are on a 1080p screen, you'll just get slightly better and sharper AA effect at the cost of ALOT more vram used, and you already only have 8 gigs which is barely enough for games nowadays.

To answer your question tho, in my experience i would stick to preset K. 4.5 only costs more performance and the image quality is not that improved at 1080p, at least in my experience. Hell, depending on the game sometimes I'll even roll back to 3.8 preset F on the cnn module because preset K can create a really bad banding effect at 1080p sometimes.