Does parrying when dual wielding shields trigger the effects both or only the one in the left hand? And what are some good shields/armor to use for such a build?

So from my testing, I'm pretty sure it's only the shield in the left hand by testing with the everfrost and duelist's shield, but maybe I'm just bad. alongside this, what shields are good to find throughout the acts for dual wielding shields? I already feel op in act 1 with duelist armor and the triple damage perk, but I know this is still just scratching the surface.