Answers to your questions about Marketing Cloud Connect for Marketing Cloud Engagement encryption.
What Versions of TLS Encryption Protocols Are Supported by Marketing Cloud Connect?
TLS version 1.2 or higher is required.
Previously, Marketing Cloud Connect has recommended deactivating the "Require TLS 1.2 or Higher" critical update. As of February 2017, deactivation of this critical update is no longer required as the integration is TLS 1.2+ compliant. No impact or actions by the client are necessary to ensure that the integration continues to function.