I have a vog cub coat, Divine Veil for shadow and elemental monsters, barbarous thorn shield (with elemental medium uv) for piercing and elemental monsters, and skelly shield for undead and fiends. I use guns and mainly swords.
But which piercing helmet is best for this loadout, skolver cap, virulisk mask, or royal jelly crown?
-Pery
IMO, of the ones you just listed, Skolver Cap is the only one that should even be considered. You should also consider Justifier Helmet for Gun Attack Speed Increase, or even Mercurial Helmet if you're into Movement Speed Increase (plus the very useful Shock resistance).
But if you were going to pick one of the three you listed, then Skolver Cap. Deadly Virulisk could be an option but with the arsenal you just listed, Skolver would be more useful.