The higher item level of anything vs an opponent that is lower will make you weaker in a sense if it doesn’t have separate stats. However essences system like Azerite will do way more damage. I responded to this in another thread.
Well of course the higher any item level goes up it tries to scale you down. The thing is essences are like Azerite. So if you have a really high neck and lower gear that isn’t socketed your essences will hit harder. Since higher item neck greatly increases the power of the essence.
Just like having a Drest trinket lowering your item lvl will make the Drest hit harder. Which is where this system can be really abused as you can combine certain things to make really wonky geared 1 shot builds.
So things like Azerite, Essences, Trinkets you want to be high as lvl as possible ( in most cases ) if they do dmg. Nothing changed there really.
Rextroy did do naked 1 shots and trinket 1 shots using lower gear. So it’s just about manipulating the system around what you want to pump.
Now we go down a road of really weird test to try and Min/Max like a CoD arms warrior his CoD probably hits way harder if no gems. The proc should do way more dmg if he is lower item level.
Does Blizzard really want us to have to test all this for BiS gear sets? Mind blowing.