” I mistakenly assumed this was all Lubavitchers, but it is clearly not your camp”
Apology accepted. Though, all Lubavitchers I know of, even extreme Mishechistim study Gemara Leiyuna with all the standard Meforshim, and learn Yore Deah with the Nose Keilim as I described elsewhere.
Tradition has it, that the Alter Rebbe wrote on all of Shulchan Aruch, and there was a fire as so often happened in those times, which burned much of his writing, including parts of the Shulchan Aruch HaRav, and a sefer entitled “Sefer Shel Tzaddikim”.
Regarding how we pasken when there’s variance between the Shulchan Aruch HaRav and the Piskei HaSiddur, much has been written about it, but in short, we Pasken like the Siddur, as it was written last.
For further reference, see Rav Chaim Noehs “Piskei HaSiddur”.