Joining a project does expose some identifying information about you to the project volunteer administrator. It may also expose non-identifying information about you through the project’s Public Project Website (should it have one).
The project volunteer administrator can see your results and some of the information listed in your myFTDNA account such as your contact information. The project volunteer administrator will not be able to see your password.
Projects often set up a website on which member results are posted. How these results are identified is up to the project volunteer administrator. Results are often listed by the participant’s oldest known ancestor, kit number, or last name. You may wish to discuss what information will be available on the project’s website before joining a project.