For my workflow, I do most everything in 3D. I often start by making simple 3D representations of my units in a class I call "shell." This is equivalent to sketching. I'll use the shell as a guide to create accurate 3D models with different classes for different materials, such as plywood skins, wood frame, metal frame, trim, etc, and eventually turn "shell" off. I tend to put each unit of my stage set (each wall or platform, etc) in its own designer layer. I can use unified view (or design layer viewports in some cases) to see the whole set together. Then I can use visibilities to create sheet layer viewports that can display each unit individually, or show just the frame, or whatever.
I don't get into symbols very much, but they could be useful to create a very clean ground plan by creating a simple 2D symbol attached to the 3D unit.
I will sometimes do a 2D detail drawing if I can't get a clean looking view of the 3D model. Often I'll create the 3D view in a viewport, draw over it in annotations, then turn all the classes off so my drawing is all that is visible.