Persistence

After reading persistence I had a question regarding its use for the following 2 weapon styles.

Unarmed fighting (brawlers)and 2 handed weapons

How does the disarm work if using either of those fighting styles or would you just take the daze version of the skill?

In order to use Persistence, you need to succumb to the status effect. If you cannot succumb to the status effect (e.x. you are already suffering it) you cannot use Persistence.

Regarding weapons wielded in two hands: if you willingly take an effect, such as Intercepting or afflicting yourself with a Disarm (by using Persistence), your Immunity to that effect does not apply. So if you use Persistence in the way which would render you Disarmed, you must take the Disarm, even if you would otherwise be immune to it.

The one exception to that immunity rule would be Unarmed and Claws. These weapons cannot be Disarmed because they are physically attached to you. Because of this, you may not use Persistence in the way that would render you Disarmed while fighting with Unarmed or Claws.

Can this ability be used to stop piercing or casted damage.

Yes, it may be used against any ability that deals damage.