I filed under the 3-year rule and had already uploaded everything online (I uploaded new evidence almost every month my case was pending). So at the interview, all the IO wanted to see was my driver license, two of my three passports, my greencard and the latest tax return (we had just filed our taxes a few days prior so there wasn't a transcript available yet, so I brought the entire tax return since it was too many pages to upload).
The interview was only a bunch of small talk, 10 civics questions and the reading/writing test. It was on a child's level (stuff kids learn in school at a very young age), very easy. The small talk is where they actually see how good/bad your English is, how much you understand of what they are saying/asking, if you can follow the conversation and give proper answers etc.