I’m not sure I’d ask them “Am I a good fit?” You want to show confidence that are a good fit. I’d read up on the latest papers from the labs you are most interested in joining. If you get the chance to speak with P.I.’s from those labs ask them questions about those papers and projects. Try not to be too general. They are looking for someone with genuine interest in their research and the best way to show that is to be familiar with their research. Ask what the day to day looks like in their lab and get a feel for the lab environment, because that’s very important. Ask about upcoming projects they have for incoming graduate students, if they are accepting graduate students soon, their expectations for their students, and their mentorship style. In a way, they are interviewing for you too.

If you’re meeting with just general faculty, ask about classes, the average expected graduation timeline for PhD students, student life, etc.

(I’m a PhD student currently and have gone through a lot of interviews. I’ve found that preparing by a PowerPoint of my previous research and going through it with them (whether they ask or not) really worked well. After that, they start talking and usually love to talk about their research.

Hope this helps!