Not sure what you mean by this. You also say that I should not use game techs, yet you say that Skyrim is the official lore when isn't that the same thing as using the game techs?
Game Techs is how you play, and such. These should never be taken into consideration. What should be is stuff that happens in the game, such as the Main Quest, as well as 'common' stuff.. Like Destruction Magic.. How you use the magic is just game techs but in general, the ability to use fire, frost, and lightning as a magical attack is considered as lore since it is common enough.
As to stay on Vampires, from my years of experience.. The common stuff about vampires that should be lore is them being weak to fire damage and have some sort of weakness to the sun as well as being skilled in certain magics. (In all TES games where you become a vampire, you at least have some sort of weakness to fire and sun as well as having some sort of boost in magical skills).. Skyrim has a weakness to fire damage as well as an Illusion boost. It also has a weakness to the sun where you cannot regenerate, so it is sticking to the common vampire lore in my eyes.. As for feeding, yes this is common knowledge lore. Vampires always need blood and I don't think there is an official way of how they do except just drink it from a bottle/neck.
Now as for Volkihar Vampires... They have same stuff as common vampires, which all vampire clans do, but also an addition thing. To me, I believe the Vampire Lord form and abilities is what unique to the Volkihar Vampires and that is what truly makes them Volkihar.. And that is what I think is the 'official', or correct, Volkihar Vampire Lore.
As about where they live.. Common Vampires normally do live in caves but the Vampire Clans normally live in their own special areas.. Berne and Quarra of Vvardenfell lived in Dwemer ruins, which can easily be found just by looking for the towers.. The Aundae was in an Ancestral Tomb, which is more like a cave but still isn't... So why do Volkihar have to be in an icy cave? Cause of a book? No. The Volkihar Vampires could've been ANYWHERE until this add-on came out.. Now we know that their lair is really a castle isolated on an island.