They can show structural details of standard conditions, things you find in code books. If you are trying to build something outside the books, an engineer is needed.
Not true, at least in Michigan and most other States..
Michigan law:
(2) If the overlapping of the professions of architecture and engineering is involved in a project, a licensed architect or licensed professional engineer who seals the plans, drawings, specifications, and reports may perform services in the field of the other practice if the services are incidental to the architectural or engineering project as a whole.
(3) A licensee shall not seal a plan, drawing, map, plat, report, specification, or other document that is not prepared by the licensee or under the supervision of the licensee as the person in responsible charge.