Before setting up profiles first finish setting up your account. Tesla supports two-factor authentication (2FA) for Tesla accounts. You should enable 2FA on your account to help prevent someone from hacking into your Tesla account. If your Tesla account is hacked someone can add additional key cards, locate your vehicle, change the account settings including password.
Tesla 2FA requires one of the following: Google Authenticator, Microsoft Authenticator or Authy (uses the Google Authenticator and adds some useful enhancements such as an optional recovery password if you have to restore your Authy credentials, i.e. restore Authy credentials to a new phone.) If you have never used an authentication app before it is very easy to set up. Download the app of your choice to get started. Tesla has information on how to turn on 2FA on your Tesla account. Once you log in to your Tesla account using the Tesla app on the phone, unless you log out of your Tesla account you should not have to re-enter your credentials to use the Tesla app. (When you want to log into your Tesla account on the web, i.e. to check on the status of your order, etc. or to order items from the Tesla online store you will need to enter the code provided by the Authentication app that you installed on your phone before you can access your Tesla account.)
This leads to the answer to one of your questions; each user should have their own Tesla account. Once you have set up the primary Tesla account you can add additional users to the Tesla vehicle.
By default the Tesla has one driver profile. You can also create an Easy Entry profile that positions the seat and the steering wheel for easier entry and exit from the driver's seat. You can create additional user profiles. The Tesla vehicle can associate one driver profile with the phone. If you use the card key the Tesla vehicle will default to the last driver profile that was used.
Bluetooth; there are two separate BT connections that are on the phone. The first is for using the phone as a key. The second is for BT streaming audio, phone. In the Tesla vehicle BT settings you can select one BT connection to be primary for audio streaming, phone calls.
