I have done way too little research on this topic of options expiration. So, by no means I am an expert. However, I have noticed three things: 1) OpEx days moves are not anything particularly bad or scary or different from other days moves "for ES". This is based on visual observation of charts on opex days. I didn't find anything extraordinary in them for ES. 2) However, individual stocks charts they are definitely different in a major way on opex days. 3) On a gaptrading website, they looked at how gap fill probabilities differ on opex days, and found opex days made no difference to gapfill probabilities for ES. So, based on my limited understanding, an opex day does not have significant influence on the way ES should be traded. Always willing to learn if someone experienced like LC or ammo or someone else can point me to somethings about ES on opex days that I have not noticed.
i am also not an expert. just something i picked up along the way. it def has an influence on individual equities not only on opex but also earnings days. i guess the theory is think like an option seller when using it, what price level would you be trying to protect.