بسم الله الرحمن الرحيم
Yes, qasr is wajib on musafir. You offer qasr salah when you are a musafir, it is ok. However, it should be known that qasr shall be done only in the fardh salahs with four rakahs and it is when you offer alone or behind a musafir imam. There is no qasr in Maghrib and Isha salah. Also in case of offering the salah behind muqim Imam there is no qasr, likewise in sunnat and nafl salah. In case there is the situation of fear and worry, for example, you are offering salah on railway station and the train is about to arrive or it is about to leave or you are offering salah inside the train in the passage then in such a case it is better to leave the sunnat and nafl. But if you are in the state of peace and feel comfortable then it is better to offer sunnat etc.
Allah knows Best!
Darul Uloom Deoband
This answer was collected from the official ifta website of Darul Uloom Deoband in India.