This is a topic that comes up at the user group on a regular basis. I think that you have to find a way that suits your style, but I do have some advice to help out. Many people put all the annotation in the viewports, and I have tried that but for me, it doesn’t work. I like to put all my annotations on the design layers, and this works for all the plan or 2D viewports, but this doesn’t work for 3D viewports.
So the answer about putting annotation on design layers or viewports depends on what you are trying to show and what you have drawn so far.
For plans, I recommend putting all the annotations, dimensions and detail references on the design layer, the same design layer as the walls.
You can make several drawings from the same wall layer if you use classes to filter the information.
For example, you can draw the foundation plan on the same layer as the walls. By putting the foundation walls on a class and putting the foundation dimensions and detail references on the same class, you can turn off all the other notes, details and details references and see the ones for the foundations.

By putting all the other walls on classes and putting the framing dimensions, notes and detail references on the same class you can turn off the foundation walls, detail references and notes, leaving the framing plan the way you want.
These two example examples show that it’s better to include your annotation on the design layers for plan type drawings, or for drawings that are 2 dimensional.
For drawings that use the 3D parts of VectorWorks, it’s better to include the notes and dimensions in the Annotation part of the viewport.
In this example the elevations and sections are live views of the building using a front view for the elevation and using the section viewports for the sections. In this example you have to put the annotations in to the viewport, there is no other way. If you try to put the dimensions and text on the design layer it will not show in the viewport.