I've read a little bit of Vance and quite a lot of REH Conan and I don't entirely get either of these mechanics. And to the extent that I do get them, reading Vance and REH hasn't made any difference.I dare anyone to read Vance and not "get" the magic system. I dare anyone to read Conan and not "get" the combat system.
The 1st ed magic system doesn't have the feel of Vance at all - strange laboratories, vat-grown creatures and ancient magical formulae that are taxing on the mind of the user play almost no role in the game. Perhaps the laboratories and the formulae are lurking there in some backstory, but they don't actually feature in game play at all, most of the time. And memorising spells is a prelude to playing the game (a bit like buying your fighter's armour and equipment).
And as for the combat system - with one-minute rounds, the typical Conan fight would last a round or two at most.
This is not to criticise AD&D or its relatives. I played AD&D 1st ed and Moldvay/Cook D&D for several years with great enjoyment, and the fact that I now prefer other systems is a comment on me, not on them. But reading authors like REH and Vance has no effect at all on my interest in or appreciation of these classic forms of D&D.