When deciding which SignRequest plan would be best for you, you'll need to be familiar with the concept of "users" and "licenses".
User: A user is someone who has the ability to send out documents for signature. For the number of users you have on your "team", you will need that same number of paid licenses.
License: A license refers to a paid subscription for 1 user. If you are the primary account owner of a SignRequest account working with multiple team members, you'll need to make sure you purchase the appropriate number of licenses according to how many users you have.
*1 User (on a paid subscription) = 1 License.