For macs, I think that might be more related to the SMB implementation. I don't have any, but I've heard of others without the same setup as you having issues with it. Macs will use NFS quite happily, and you can probably save yourself a headache if you just set them up an NFS share.
As for the weirdness with setting CIFS up in CDOT, what we do is use an administrative user that literally doesn't have domain rights except joining a computer to a pre-existing computer account in a specific OU. When I "unjoin" the domain, it gives me an error that it can't delete the computer account, but will actually disable CIFS on the SVM. A hack for that is you can deliberately provide an incorrect password and it should still ask you if you want to continue without deleting the computer account.