Which model within the dgn am I supposed to design, annotate, or print?
DESIGN: All design work should be done within a 2D Design Model unless you are creating a terrain dgn or processing survey data. Those should be done within a 3D Design Model in a 3D dgn file.
ANNOTATION: All annotation on the design should be done within the Drawing Models. The Design Model is referenced to the Drawing Model. Annotation is not done in the Design Model. Title Block annotation is pulled from the Drawing Seed you specify when creating Named Boundaries. This video goes into Title Block detail: https://communities.bentley.com/products/road___site_design/w/road_and_site_design__wiki/37461/video-how-to-add-sheet-index-number-annotation-to-a-title-block.
PRINT: All printing will be done from the Sheet Models. The Drawing Models are referenced into the Sheet Models.