Some important complications are missing

When changing a complication from another watch face, there are several more complications available to choose from when compared to the ones available for a complication made in WFS. Please see the attached images of another watch face’s choices including heart rate and water. While the choices in the WFS complications only include steps. There are many others as well that are not an option in the WFS choices. Are these possible to make show up for a WFS built complication?

Is your first image for short text complication? I have used a small image complication and it was provided me the same customization option like your image(Body oxygen, Breathe, Daily activity, Heart rate etc.). But for short text complication only steps option shows.

They should all be the same complications if this is the same API level
The complications available in Watch Face Studio are standard and should be available on all smart watches API 28+ any others have to be installed by the User.

Not all apps have complications for all types of complications.

Samsung Developer Relations