Tonhi,
this is my experience: just on Dec-11-2023 we have an interview , they asked general questions, Name. DOB. what you both do..ect..
they didn't ask for anything that you are bring the interview. got a blue slip asked for family Tree and Timeline of your relationship.
we submitted all and 4-days later got a new letter that we are in AP. no further docs required. it's now almost 4-months I sent an inquiry on March-4 and got an email back from them on March-28 said: the case is still under AP. they will let us know the outcome when it available. DO NOT need to contact them anymore. ( another word just shut up and wait stop asking )
My thought after this: they already have your case approved before you get there, if you have upload everything with your application from the beginning then you should be good. again every case is not the same, I know someone just asked 5-questions and got approved. Just go to the interview and hope for the best. there is no way anyone known what the officer looking at.
wishing you the best of luck.
oh BTW don't worry they are not go to anyone house to check with K-1 case ( CR-1 yes one person that I know )