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
In this game, your priorities on armor should be
1. offensive bonuses and movement speed
2. shock, fire, maybe freeze resistance
3 damage protection
4. other status resistances
If you're in a highly dangerous situation (Firestorm Citadel for the inexperienced, Heart of Ice, Shadow Lairs), then you may switch #1 and #2. But in most situations you can avoid getting hit with shock and fire, and your goal is to kill as quickly as possible. #3 is less important, because its practical effect is so small (one more hit before dying, maybe). #4 is less important because you can deal with those statuses pretty easily. But you can switch #3 and #4 if you want.
With this in mind, the only piercing armors worth considering are the ones that Dibsville mentioned.
Your armor protects you from fire and shock (curse is rare) and your shields cover Pierce or Shadow/freeze/poison.
You have no stun or freeze protection so I suggest Ironmight, Justifier, Royal jelly, Ice queen, and Skolver to cover these gaps. Ice queen fills these gaps but has no offensive boost and is harder to obtain.
Justifier and Skolver are good offensive choices while Ironmight and Royal jelly make for good defensive choices.
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.