Based on what I saw, I think McNeill will be able to handle 3-tech early and give us a better run defender at the spot than what Gallimore provides. He's not considered ideal as a pass-rushing DT, but I believe that he can collapse the pocket some and he and Shelvin would be a handful for the offensive line clogging up the middle.
I really think McNeill is going to be a better pass rusher than some expect because (at least in my scenario) he would get more one-gap responsibilities instead of being the guy expected to take on the double-team. That's going to allow him to collapse the pocket, which we badly need.
However, I don't really care how Dallas decides to beef up the middle. I'm going off clips I've been able to find that generally focus on the player's best moments. I just want the Cowboys to seriously address the DT deficiency. If that means they feel Davyion Nixon is a better choice than McNeill in the second round, I'm fine with that. Same with Tuefele or Onwuzurike. I like McNeill better, but what do I know.
I like the idea of double-dipping early because I want to adequately, or even more than adequately, address the DT issue. I'd rather have too many good players there than not enough. You can plug in different names if you want, but I just want us to take two of the best DTs in this draft. The site I was using has McNeill as the second-best after Barmore (and available when we pick) and Shelvin behind Marvin Wilson and Nixon (who both would be gone based on those rankings).
In fact, Shelvin was rated slightly ahead of our pick, so I gave myself some leeway there, If I assume that he's gone, then I'd probably want Tommy Togiai as my second early DT. He was rated 78th, while Onwuzurike and Osa Odighizuwa also were there and rated slightly higher (75 and 76).
It's really impossible to know if the teams have similar ratings for these players.