My native resolution is 2560x1440 @60Hz. I want to boost the resolution through Dynamic Super Resolution Factors but I am not sure what level of Dynamic Super Resolution to choose. Also, what level of Dynamic Super Resolution Smoothness should I use?
Same as with any other display resolution: Best is 4x and smoothness 0. That results in 5120x2880, which is twice the pixels in each dimension, meaning four times the overall pixel count. As you can imagine, It's gonna hurt frame rates immensely, unless you're running an old game or a very lightweight one. If you use anything lower than 4x, you probably need something like 20% smoothness to somewhat smear up the scaling distortion. In my experience though, anything lower than 4x does not work that well. The amount of AA you get is way too low.
Per above, while i can't comment on going from 1440p when using 1080p 2.25x and 15-20% was what i had good results when playing Witcher 2 with DSR. 4x looked great, but unforntuntley 60fps min was a no go, and anything inbetween just looked bad.