Tricky Boutique Situation - Advice Needed

I am new to this site and find it tremendously helpful. I recently just interviewed with a small shop boutique investment bank and had the final round earlier this week. The partners seemed to like me and they informally told me that they would be happy to take me on. They did mention that they would need to contact some of my past employers after the interview.

The problem I have is that I also have several other interviews with various boutiques in the area. The shop I interviewed with already though is my top choice, but I have not heard back yet on whether or not I would be getting a formal offer. Should I continue to interview with these other shops and what should I do if I am asked to sign on the spot (one of them is tomorrow and a first and final round within the same day)?

I am not sure if I should just ask the boutique I interviewed with when I should expect to hear back.

Thanks!