Bismillah i Rahman i Raheem
Assalaam o 'Alaikum Wa Rahmatullah i Wa Barakaatuh
I was recently listening to a part of a Majlis and learned that Nafilah, or generally Mustahab prayers may be offered without standing, without facing the Ka'abah. This made me think, that if one would like to offer say, the Nafilah of Maghreb, then will he only pray the prescribed number of Rakats or will he double them if he prays sitting down? I am aware that the 1 Nafilah of Isha is to be prayed as 2 Rakats while sitting down as an obligatory precaution. What about Salat ul Layl, can one perform all of it without facing the Ka'abah and not standing up? If so, will he also need to double the number of it's Rakats?
Also, does this also mean that say, a 2 Rakat prayer of Shukrana (thanks) may also be prayed similarly (as in not facing the Ka'abah, not standing up) with/without doubling?
JazakAllah
Wa 'Alaikum Assalaam Wa Rahmatullah i Wa Barakaatuh