Many undergraduate and graduate physics students participate in some form of public engagement throughout the course of their studies, often through groups supported by physics departments and universities. These informal teaching and learning programs can offer unique opportunities for both participants and facilitators to interact in a way that fosters physics identity development. Understanding how physics identities can be cultivated will allow us to work toward a field that is inclusive of more identities. This study builds on previous work to investigate facilitator experiences in three informal physics programs using an operationalized communities of practice framework. It utilizes the intersection of community dimensions and mechanisms of identity from the communities of practice framework to analyze three different informal physics programs. Through analysis, the authors identify different structures within these programs that support physics identity development. The results are complementary to findings from previous studies that showed informal physics programs can provide growth opportunities for university physics students in specific physics practice, such as improved scientific communication skills and pedagogical modalities.