I definitely agree with your concept of averaging a few ranking publications. I was just lazy, and selected Massey’s site to quickly review every team’s opponents. Originally I was curious how many non-D1 teams everyone played. Then I got side tracked by how many 300+ teams there were, so I lumped them in too.
After checking the NET, or Kenpom, or another site, I also like to review the following compilation. More publications are added to the table as the season progresses- it’s up to 50! Even though I’m not familiar with most of them, the big hitters are all there, and for me the average is a good gut check.
https://www.masseyratings.com/cb/compare.htm
FWIW, I think the quantity of non-D1 schools is an example of why the rankings are so different from one site to another... sometimes those scores are used, and sometimes they aren’t.
I remember you saying that some team (I couldn’t recall which) always scheduled 4 or so non-D1s. It’s what prompted my post.