For whether it is I or they: so we preach, and so you have believed.
Therefore whether it were I or they, so we preach, and so ye believed.
So, whether then it was I or they, this is what we preach and this is what you believed [what you adhered to, trusted in, and relied on].
Whether then it be I or they, so we preach, and so ye believed.
So then, whether you heard the message from me or them, this is what we preach and this is what you have believed.