The Big 12 and the SEC. I know everyone gives the Big Ten West a hard time for being so bad and rightfully so but it's crazy to realize the Big 12 is even better than the Big Ten East. Really it's the Big 12 and SEC and then everbody else way down the road
https://www.usatoday.com/sports/ncaaf/sagarin/2019/conference/
https://www.usatoday.com/sports/ncaaf/sagarin/2019/conference/