Help with penance brand inquisitor

Hello,

Harvest is only my second league and after starting with a stormbrand inquisitor, I tried to switch to penance brand. Sadly, I haven't found any guide so I tried to copy this build:

https://poe.ninja/challenge/builds/char/plowce/JuicyBrandin?i=49&search=class%3DInquisitor%26skill%3DPenance-Brand%26allskill%3D!Brand-Recall



I have two issues:
- I don't know when to use penance brand and when to use arcanist brand.

- I don't get how it is possible to run hatred, herald of ash and herald of purity at the same time.

If you guys know a build guide, I'd be delighted but just answering those two questions would be really cool too !

Penance for packs, arcanist brand with wave of conviction - single boss.

You can run three auras after you pick Eldritch Battery passive. You will spend energy shield instead of mana for skills.

Mathil doing this build, you can find POB here https://www.pathofexile.com/forum/view-thread/2880284

And he explains a lot at youtube channel - https://www.youtube.com/user/Mathilification/videos

Well, WoC was fixed so the damage is not OP anymore.