McNair always put up numbers like 15-27 for a 170 yards and like 30-40 yards rushing. He had a prime Eddie George and Jamal Lewis with high quality olines with players such as Bruce Matthews, Joanthen Odgen etc. Similarly, to us with Zeke and our oline. The most tds McNair ever had in a season was 24. I think this is the best comparison you can make for Dak. He's not Mcnabb. He's not Russel Wilson. Etc. Opinions
If you saw "AIR" McNair in college before Fisher reeled him in with that prehistoric offense (see Vince Young), you would never compare "AIR" McNair to Dak as a passer. McNair was much better as a pocket passer at all stages (college and pros). In fact McNair's pro stats TD/Int are better than Aikman.
However, since the Cowboys have a simplistic offense, the body types are similar, the heart and passion are similar, the ability to run (McNair was faster) similar, I agree with those parts of your comparison. But Alcorn St. "AIR" McNair was a gun slinging running scrambling QB. YouTube, Wike, and Google Air McNair and you will see as a passer there is no comparison on any level to Dak as a QB.
I grew up in LA and got to see McNair a lot in the SWAC. He reminded me of a bigger stronger faster Roger Staubach in College. I never would make that comparison of Staubach and Dak in college. You are what you are; Dak was a 4th round pick vs. Air McNair was the 3rd overall pick in the NFL draft.