Thank you! It ended up being really laid back!
For international students who have skype interviews before being invited to weekend interviews, stay calm!
My interview was mostly to see that I was actually interested in the school, and there were more personal/laid back questions asked. They did ask about my research, but that was a short part of the conversation.
Be prepared to ask questions and explain why you want to go for their PhD program. At this point, they know you're a good student, they just want to know more about you as a person. At least that was the case for me! Good luck to everyone!