For the tone curve fine adjustment, try holding down the Alt/Option key as you drag a curve point.
The brush size adjustment could more likely be a preference in the touch-pad setup, as it would for a mouse scroll wheel.
Same issue, even on version 6.7 and official release of MacOS Sierra...
Same issue here on my system (Sierra, latest official release). Tried to reinstall creative cloud, lightroom, drivers and so on. Still the same problem!
There is an other thread active here, with the same theme.
I'm having the same issue with curves now that I've upgraded to macOS Sierra. Anyone find a resolution yet?
nope dont think so 😕