Mine has been well over 100 and no issues. High e2 doesn't always mean sides, that's where bloods come in handy... However, even if it's high, that doesn't necessarily mean you're in trouble.
Low E2 on the other hand, I don't think anyone gets away with no sides when estro is tanked.
Best way I can describe the sides I get is like having a bad case of the flu. I've gotten nauseous, everything hurts... Hair, skin, joints. Just overall discomfort everywhere. Hot then cold then cold and sweaty.
I don't even remember the last time I took an AI. If I have an issue, I take nolva.. otherwise, I'm g2g.