Question about penetration, please help

Hey everyone, I was wondering if anyone can answer me on this one. Thank you so much for the answer (playing lightning frost claw)
720hours in game and I still dont know the answer 100 percent correctly to this one

Lets say this is my flat damage for example
100 lightning damage

Armor shred is basicaly reducing armor to the enemy does armor as well protects from elemental damage, or only physical?

Lightning shred resistance, this one is doing same as armor shred but only to lightning res, but what is the difference between them and more importantly is it beneficial to have both of them if I have 100 flat lightning damage?

Shock chance - this is the same as lightning shred?? I really dont get it, if so is it benefical to have shock chance, lightning shred and armor shred on the same build if your build is pure lightning damage? (this one is the most confusing for me)

Lightning penetration lets say 10% is basicaly giving me 10 more damage on 100 flat (lets exclude crit chance, multi and other which are comming in calculation before penetration itself) - am I correct on this one.

And the last question is lighning pen coming last for damage calculation after shred armor, shred elements and shock?
And if you have examble 100 light damage what of these 4 should you invest in and is it beneficial to have all 4 of these lets call them sort of ailments

Thanks so much everyone

Armor mitigates non-physical dmg but only at 70% efficiency.

No. You need both.

Armor shred decreases enemy armor by 100 per stack. It doesn’t have a cap. You wanna have as much as possible with diminishing returns kicking in at about 40 stacks (afaik - correct me if I’m wrong) so if you consistently see those stacks, getting more will be beneficial but less so.

Res shred is reduces res by 5% (2% for bosses) per stack but is capped at 10. So you don’t need a lot of it, just to keep that 10 stacks going.

Basically, yes. But (afaik - again - correct me) it stacks on top of lightning res shred and has some other benefits (stun chance iirc).

I don’t know how resistance values affect actual dmg numbers.

The big distinction is that all the above (shreds and shock) are debuff stacks. You apply them on the enemy, and they mess with their stats. Penetration is not a debuff, it’s your character’s stat. It makes dmg go around given amount of enemy res.

Yes, it’s beneficial to have all of them. Which one is best, idk. It depends on the opportunity cost.