(1) It is not right for a Hanafi follower to offer witr salah behind the Imam who leads witr prayer with two salams. The iqtida shall not be right.
قال فى الدر (مع الرد كتاب الصلاة باب الوتر والنوافل 2:444 ط مكتبة زكريا ديوبند): وصح الاقتداء فيه ….. بشافعي مثلا لم يفصله بسلام لا إن فصله على الأصح فيهما اهـ
So if your Imam leads witr salah with two salams in the month of Ramadan then you should not offer witr salah behind him. In the same way if in case of leading with one salam he does not do qadah knowingly on a regular basis then too you should not offer witr salah behind him. As the first qadah is wajib according to Hanafi Fiqh and salah is makrooh tahrimi when wajib is missed knowingly and it is necessary to repeat the salah.
(2) If Qunoot Nazilah is offered in Fajr salah then you too should say Amen like other muqtadis folding your hands. And if Qunoot Nazilah is offered in any other salah except Fajr then you should stay silent leaving your hands. So it is mentioned in al-Dur and al-Radd, Vol. 2, p. 446, 448, 749.
Allah (Subhana Wa Ta’ala) knows Best
Darul Uloom Deoband