My interview felt generally a bit disorganized.

A few people who were scheduled to interview didn't show up. In one instance, several people were present for the same interview due to scheduling mishaps.

There was a mix of program managers, EEs, and MEs on the panel.

They did feed me lunch, and the recruiter was very informative throughout the whole process.

Be comfortable and be yourself.

Let them decide if you fit the job requirements, as opposed to trying to shape your skills to match the job description.