Can people outside my team submit information?

Yes. Public forms let people send you records without an account, and submissions can be anonymous.

A stranger can only fill in the fields the form asks for. This is worth being precise about, because it is where most tools are weaker than they look. Hiding a column on a form is cosmetic - anyone can read the page source and see what is there. In Bionic Forms the server refuses a field the form did not ask for, so someone who guesses the name of a field you did not put on the form still cannot set it.

Permissions are set per person, and guests can be limited to form access only.