He meant "steel", not iron... but yeah.

-Loth
Yeah, I worked it out. But that is kind of the point, he is not even talking about steel weapons, but skyforged steel or nord hero steel. It cuts down on the weapons you can choose. I actually really like the armour cap because with some effort you can wear fur and have no real handicap. To use daedric or glass weapons we have the slightly perverse situation where w need to invest more perks for the same damage outcome.
Going elemental is just another way to be able to use whatever you want/whatever looks good/whatever fits your character. I think for that it deserves a thought.
I don't love sneaky characters, but I might test a pickpocket character to find max 'reasonable' damage via poisons. I already have a good character set up for it. Is there a cap on negative resist?