Clarification on Key exchange approaches in TLS/SSL
are the DH public values exchanged unencrypted?


Yes, that are.  After all, they are "public values"; there's no weakness in exposing them in the clear.

Now, we do have to be careful that they aren't modified in transit (if they can be, then someone can perform a Man-in-the-Middle attack).  We do that by having the server sign its key share (using the private key of its certificate).