Since the Google Ads API uses an entirely new protocol for communication, many of the concepts you may be familiar with from the AdWords API are different. This page outlines the things that you can leave unmodified from your previous implementation.
Developer tokens are still required for using the Google Ads API. The limited number of operations for Basic Access still applies, and the process for applying for Standard Access remains unchanged.
You can use the same developer token that you used with the AdWords API, and whatever level of access you had for the AdWords API will carry over to the Google Ads API.
During the initial beta stages of the Google Ads API, you will need to apply to have your developer token whitelisted by filling out this Sign-up Form.
The requirements for authentication remain the same. The Google Ads API uses OAuth2 for authentication, which requires an access token at the time of the request. You can re-use your existing refresh token, client id, and client secret that were used for the AdWords API without any adjustments.
If you need or would like to set up fresh credentials, check out the OAuth guide.