Not quite. Each role has different access to different areas of the account. More info can be found here, in the user guide.
What you can do is grant yourself Admin privileges, which gives you access to all of the Account Manager actions, and then you can make yourself a Designer.
The purpose of Account Manager is to have role that is solely for account management, with no need to access prototypes or the cloud functionality. Mainly the role is used by larger companies.
Let me know if you have any questions.