as to the OP, I don't see anyone projecting Williams as a 4-3DT at all, 3-4 NT only
4-3 DT is really his natural position and the one he is best suited for. He played DE as a junior and was only moved to Nt as a necessity as a senior. He's a little light for 3-4 NT.
As far as Jenkins goes, he'a a terrible fit for a 4-3. He gets no push on pass rush and is way too easy to move for a guy his size. He got manhandled by a guy on one leg in the SECCG.
The saints don't need a gap eater near as much as they need a playmaker on that side of the ball. Imagine Aldon Smith in black and gold