The short answer to this question is: No.

OAuth access does not inherently offer greater security compared to Manager (MCC) access.

Regardless of whether you opt for OAuth or MCC access for your Google Ads account, the individual or organization granted access will possess full privileges to view and modify your data.

The primary distinction between OAuth and MCC access lies in the fact that MCC access additionally allows interaction with the Google Ads user interface. However, in terms of data security and access via the Google Ads API, both OAuth and MCC access provide equivalent levels of access to view and alter your data.