Straightforward question: For a 2 person founding team, are they both cofounders, is one a founder, or is it situational?
Just cofounder. Co- prefix just means amongst people. Like, your coworkers are also workers. But in your context, they're coworkers. It's weird to say "this is my worker" instead of "this is my coworker" when referring to someone you have a common relationship with.