You are right there must be differences in weapon types.
But at the sametime I don’t know if in an Arpg we can expect too much on the exact physics of items.
I would love to go all out and for the people that played Pen and Paper games, Ice Law tables had Weapon versus Armour so to put it simply a Dagger has to do less damage to someone wearing Plate as they should know how to move in it and in doing so take less damage, but Crits had ways around it. A high value Crit could say. A brilliant move, you found a gap in the Armour and puncture a Lung.
The other point is true with I think a War Mattock, it’s a short version of a halberd the spike that could puncher Plate and deal more damage.
It compounds damage by using Crit Tables and I know D100 or percentile Dice are not an option here, but Crits had Puncture, Fire, Blunt even Tiny Animal attacks and many more.
A ranging from A-E, a simple and short version here.
0-20 low added damage 29-65 medium 66 some extra and an odd effect 67-99 high damage added, with 100 almost always out right kill in some gruesome way. Each of them adding a flavor text.
The A-E range on the first table was based from your Attack versus the opponents Defence giving you a total to check on the table.
So after you rolled and got your total, the table may have a few or many 0-1 damage moving up to say 2-5 and at some point 5+A crit all the way up to say 30+E Crit.
Weapons even had Fumbles but that’s even more complex.
Maybe if I have a Point here at all it’s even though I would love to see this much complexity, I don’t see it happening here, as long as it’s not to simple just for the sake of it.
Maybe a simple way to do it is Robes have no speed debuff same for basic leather but as you add bolk and weight up to say plate there is a small 2% debuff to your movespeed.
This could add a layer of itemization, if a magical Robe had high def of some type there is a small movespeed debuff -1%, in the Plate Magical properties it cancels out the Debuff of normal Plate so you have no penalty.