I really with that browsers didn't autocomplete ever. I've had instances where they will happily auto-complete my entire credit card number. Usually, they'll only memorize the first 4 digits, but sometimes they memorize the entire thing.
For me it pops up a little box under the input asking me to choose if I want to autofill. I like this option because it doesn't autofill without permission but my info is still saved and easily accessible.
autofill actually annoys me, which is why it's one of the first things i disable when setting up my browser(s)