You can change the DDC setting of the Apple Studio Display 17 and Apple Studio Display 21 by using the On-Screen Display controls (described in your Users Manual).
Most newer Macintosh computer models support DDC, so the default DDC setting on the display is ON.
Important: If you have reset the DDC control, turn the monitor off and then on again by pressing the power button at the lower right corner of the monitor's front panel, then restart your computer. Doing this ensures that the new DDC setting is enabled.
The viewable image size of the Apple Studio Display 17 is 16.0 inches.