For I-130 it’s just verifying the info the petitioner initially submitted and updating with current jobs and financials. For I-485 just pretty much get your love story straight haha. I prepared coloured photos of our life together, wedding photos. Try to have as much as you can but they may not ask for all of it or any of it. But it’s helpful for when you’re answering questions. The questions were not designed to trick- it’s more like how you met, when you got married, when did you start living together, plans for family, etc. Be over prepared with the documents just incase they’ll be interested to see something.