You will be interviewed by single or multiple principal investigators, single time or multiple times. Interview are usually very casual and not that difficult to convince your Interviewer. They would easily hire you if you are confident and can portray you interst in research.

I submitted online but also through a former employee, received an email about the interview apron. 1 month after submitting, interview of 30 minutes, very friendly. Not hard questions, mainly orientated to your life project.