Is intrinsic ethos and logos essentially the same thing?

No, but the distinction is something like the difference between "all fish live in water" and "everything that lives in water is a fish."

Ethos relies on the credibility of the person making the argument. His or her reputation, charisma, education and other personal qualities factor into how likely we are to believe what the person is saying. Intrinsic ethos is credibility that comes from the way an argument is presented. For example, an essay may seem credible because the writing is authoritative.

Logos refers to the argument itself and the specific reasons or premises used to support a position. Aristotle conceived it as an appeal to logic.

A good argument that appeals to the sense of logos typically also has intrinsic ethos. On the other hand, an argument may have intrinsic ethos, or superficial credibility, even if the logos is based on unsubstantiated beliefs, poor reasoning and successful appeals to pathos (emotion). This is the heart of most political rhetoric.