Go to the interview day if money could sway you to Temple. Some of the schools that I’ve interviewer at I would only attend for a near full ride aid package; though it’s unlikely, it’s certainly possible. So, I can’t rule them out until I hear back about numbers. Alternatively, there have been a couple schools that I know I wouldn’t attend regardless of aid. Those are the ones you respectfully decline and pass the opportunity on to another deserving applicant.
I don’t think there’s such a difference in these schools that it would be crazy for you to choose Temple over Iowa. While Iowa has a strong program that’s ranked well, I don’t think the prestige gap between the two is as wide as the rankings would indicate. Iowa is undoubtedly the better equipped program, but it’s not as though we’re comparing a T20 to a low tier school. Both basically mid tiers but on opposite ends of the mid tier spectrum (figuratively). Can’t go wrong w either, but I’d go to Iowa unless Temple ends up being cheaper. Congrats and good luck!!
edit: I’ll add that I wouldn’t be worried that u haven’t prepped. My best interviews so far have been the ones I haven’t prepared for. Kinda allows you to be more natural I feel like. You’ll be fine!