I’ve been having trouble understanding what are the most recommended Surahs to read in the wajib prayers and Salatul Layl. Regarding the wajib prayers, I read that according to Sayed Sistani it’s best to recite Qadr in the first rakat and Tawheed in the second. I’ve seen others say the same (e.g. Khomeini), but then they also say for examples it’s best to read surahs like Qiyamah, Qashiyah, Naba, Insan for Fajr or for example Takathur, Nasr for Asr. So I’m confused out of all these recommendations, which choice is the most recommended? I’ve seen different recommendations for Salatul Layl. For example Allamah Tabatabai says to read the azaim surahs (I’m guessing he means Sajdah, Fussilat, Najm, Alaq) and then Allamah Majlisi says for example surahs like Muzzamil, Naba, Yaseen, Dhukan, Mulk, Insan. I’ve read Sadiq Shirazi recommends longer surahs – he mentions Anam, Khaf, Anbiya. So again I’m confused as to which is the most recommended?

Yes there are various narrations.
It’s best to have a list and recite as many as possible in different salah. In that way you won’t miss out and cover all possibilities.