I had previously stumbled across the below URL which led me to believe that there are different widths even for variable width fonts. I know that xadvance is not the same as width, but it is probably related.
I tried to pick a tall font using the ratio of x and y advance on that URL for a couple of different fonts, but maybe I should try a few more.
https://forum.arduino.cc/t/adafruit-gfx-font-size-points-to-pixels-for-epapers/556091/2