Well, that test produced some unexpected results.
The CAS option isn't functioning
at all on my main setup (haven't checked the others yet). The output with CAS selected is identical to normal, irrespective of slider setting, even after restarting the client. The only way I can get any in-game sharpening to work is via FSR.
Anyway, this is 4k custom ultra with FSR using a SSAAMultiplier of 1.0:
This Normal as well as any CAS setting (because CAS is broken here):
Images are 97% jpegs that are visually indistinguishable from the originals. They will need to be zoomed in to 100% to make the differences between settings clear.
Anyway, it's clear that the scaling is not being applied to the FSR image at 1.0 render scale, thus no additional pixelation that isn't directly due to the sharpening filter. I recall CAS looking pretty much identical at around 50% on the slider (.5 on FFXCASIntensity). As for why CAS isn't working, it could be an issue with NVIDIA's current driver.