In order to centralize power, what did the Qin Dynasty set up in the border areas for management?

In the border areas, the Qin Dynasty set up many counties, including Liaodong County, Liaoxi County and Youbeiping County in the northeast, Jiuyuan County and 44 counties in the Hetao area in the north, and Xiang Jun County, Nanhai County and Guilin County in the south. In these frontier counties where ethnic minorities are concentrated, the county-level administrative regions established by the Qin Dynasty are called "Dao". In fact, Taoism was a county located in the frontier minority areas in the Qin Dynasty, but it was different from the "county" under the inland county in name. The county chief treated the county and Taoism equally in management. In addition, the Qin Dynasty established a "vassal state" in a large area of frontier ethnic and tribal areas, and there were special vassal state laws in the Qin law; In the border areas, the titles of kings and chiefs of ethnic minority leaders are still retained, and they are called "princes" or "princes". Therefore, some people think that although there were counties in the border ethnic minority areas in the early Qin Dynasty, they were still ruled by ethnic minority leaders.