Generally speaking, one is a worker and the other is an office worker.
Requirements of assistant engineer: bachelor degree, engaged in this major for more than one year, junior college for more than two years, and technical secondary school for more than five years.
Engineer requirements: college degree or above, with the title of assistant engineer for more than 4 years. You have to take an examination of the title computer before you are eligible to register.
Specifically, you go to the title office of the personnel bureau where your workpiece is located and ask. (Technicians are run by the Labor Bureau, and there are two different units. This is the difference under the previous system. One is the labor bureau, workers, and the other is the personnel bureau, a national cadre. )