I have a scroll-wheel mouse for my Mac. So I right-clicked on Civ 6 (1.3.13) in the Steam Library window (over on the left) then Properties. I disabled the two check boxes in the General tab. I put this into the Launch Options text field (with myusername set obviously):
/Users/myusername/Library/Application Support/Steam/steamapps/common/Sid Meier's Civilization VI/Civ6.app/Contents/MacOS/Civ6_Metal_Exe
then I started Civ 6 using that Steam method (right-click, Play). I went to the Graphics Options, turned on the v-sync check box and set the frame limit to 30. Then restarted Civ 6 using the same right-click, Play method.
This seems to have helped quite a bit. The GPU is down considerably, and the CPU is similarly down. See the attached screenshot. This is Turn 1 after founding a city in the default location. The smoke and fire are still fluid, the palm trees are still swaying, and the water near the rock looks fine. Other than v-sync, the remaining settings are as per the two Ultra sliders.
However, it is clear that the developers could still do quite a bit of optimization. On this Turn 1, my GPU/CPU utilization is the same whether I am zoomed all the way in or all the way out. So they don't seem to be optimizing based on scale and it explains why Civ 6 uses more GPU/CPU later in the game even when nothing is happening. In a big map, we can't see sub-pixel swaying palm trees so there's no reason to sway them...
Thanks to all.
Scott