You definitely can wear a swimsuit, however, floating is about minimizing as much sensation on your body as possible. Some also find the addition of a swimsuit uncomfortable during their float session.
Yes, many clients come in pairs or groups. It’s great to have someone to talk with, about your experience. The float pods accommodate only one person at a time, but you can schedule your floats simultaneously.
Sensory deprivation is the deliberate removal of stimuli from one or more of your sense. The removal of outside stimuli allows you to completely focus on the present moment and can be very useful for mediation.