@rseiler I did check the fonts when looking at that Neowin page between 6.6 and 6.7 and I can confirm your findings. The fonts on 6.7 are better defined and smoother edged. It is a noticeable improvement.
When you mention the upper left menu are you referring to the Vivaldi menu. I did not see differences with a quick comparison; it is also harder to compare because you can't have both menus active at the same time. I am using Vivaldi in dark mode and I think you are using light mode which could account for differences in our observations?