All plans conform to one of the nationally recognized set of building codes. Plans are never sent out engineered. This will be true for any stock house plan you purchase. The reason is simple: every building lot has unique characteristics that must be addressed differently.
Not all areas require an engineering stamp but in mountainous areas with steep building sites, snow loads on roofs, or in areas prone to fire hazard you may be required to have a licenced engineer review, adjust and stamp your plans prior to submitting your plans for permitting.
We highly recommend that you work with your builder and his/her engineer to navigate this process. They will consider local building codes, soil condition,s and fire hazards.