>>1020723
> Should I sculpt or should I box model things that I want to 3D print?
both, you should start with hard surface modeling first.
>Zbrush or Blender for sculpting?
Zbrush is a better program, more performance and better tools, for hard surface it is not that good compared to blender but if you want hard surface Plasticity is a better option, Nomad sculpt is better than blender too.
>Is there something like the Blender donut tutorial series for Zbrush?
Getting Started with Sculpting - ZBrush for Beginners Tutorial by
FlippedNormals.