[Django]-Uncertain how to design django apps – best practices

Apps are intended to be self contained “modules” of code that could be reused in other django projects in the future. Ask yourself whether you’d ever want to re-use this code in another project.

Your extended user model, with teams would strike me as being part of a single app. You’re not defining site-specific behaviour with respect to teams or members. I could also see many cases where you’d re-use the above code.