Something has changes for the worse in the latest release.
1. This is easy to replicate and this is only happening in CC. Render a face with "Optimize with Full Screen Render" and WITHOUT Super Sampling. The render would come out squeezed horizontally. AS oppose rendering with "Optimize with Full Screen Render" and with Super Sampling produces a normal render.
I have overlayed 2 renders with exact the same camera angle "Optimize with Full Screen Render" with and without "Super Sampling" and then reduced an opacity on one of them. Screenshot 1
2. Sometimes if you export 4K with regular or small viewport, render comes out blurred. Even Full Screen renders do not come out as they should. This is tested in iClone. I did not want to create another ticket, but I suspect the same thing might be in CC. See screenshots 2, 3 and 4.