In most cases, it just blocks or hides cookie related pop-ups. When it’s needed for the website to work properly, it will automatically accept the cookie policy for you (sometimes it will accept all and sometimes only necessary cookie categories, depending on what’s easier to do). It doesn’t delete cookies.
…not sure about that. In my heart of hearts, I always want to help out fellow developers with the performance/diag data. I guess I also almost always want “functionality”.
The only thing I never want (and that “preference” is often worth leaving the site entirely if it’s not easy to express that) is the marketing/social scam. So I’d prefer the plugin to choose this for me.
I understand it’s not technically easy to do so, unless there is some standardized way – at which point we probably would not need plugin for that.