Hmm...I think your right, my Twin Souls perk doesnt work when Im a VL, I can only raise 1 dead person at a time, so probably not.
Maybe not that perk. That spell, however, is probably codded differently: it might not even count as Conjuration. Not only are gargoyles neither atronachs nor undead, but when you
can summon two, they're summoned together at once.
I know that the Avoid Death perk works in VL form. Maybe others.
I'm not sure, some perks definitely seem to be off, as your example with Twin Souks. Can anyone say if vampires naturally absorb magika? If not, then my Atronach perk still work (I don't have the stone).
Like this.
That said, I don't know whether the VL is coded as undead in the first place. Necromage probably works--that is, your spells are more effective against undead while in VL form--but whether that applies to they player depends on whether the VL form counts as undead in the first place.