Yilan can be played for two days, and Jiufen can only go to the nearby Shifen Old Street, Yinyang Sea, etc. in about one day. It is crowded and there are many mountain roads<br/>It is recommended to drive by yourself or charter a car.
If you are driving by yourself or with a friend, then I would recommend Yilan and Suao, where there are many places to visit. If you are taking the train + bus, it is recommended to go to Jiufen, and then do not turn back the same way. In the afternoon, take the "788" bus to Keelung Miaokou Night Market, and then take the train back to Taipei after eating seafood and snacks. PS. Do not go to Jiufen by car, parking is super troublesome. <br/>Hope it can help you, and wish you a pleasant journey!