I don't believe they would have been that much better at all. They are a bad team with a bad oline and a mediocre QB. Elliott went to a team with a top 3 oline, and a promising QB.
There are rare few backs in the history of the NFL that were great on terrible teams. See Walter Payton and Barry Sanders. That is not elliott.
I don't know. In 2016, they finished 6-9-1, missing the playoffs by 3.5 games. I'm willing to bet I can find 3.5 games where the Bengals could have benefited from Elliott to get them a win. For example... week 2. They lost to Pittsburgh by 8 points in a game where Bernard and Hill combined for 39 yards rushing. Yeah, they had 137 receiving, but that's the result of them not being able to actually run the ball... plus being down virtually the entire 4th Q. Note, 80 of Bernard's total yards (117), came AFTER they were down 24-9... and he had a fumble. I think that's a game they win because Elliott would have been able to get yards on the ground that those 2 couldn't, to keep drives alive and win that game.
I'm thinking the 4 point loss to the Bills where Hill and Bernard combined for 80 rushing yards is another as well as the following week where they lost by 5 to the Ravens where Burkhead and Hill combined for 50. That, plus probably being a difference maker in that tied game vs Washington puts them at 10-6 and tied with Miami, who they beat, and puts them in the playoffs. I don't think I'm really reaching there. To note, that win vs the Steelers, with those other wins I noted, wins them the division. That puts both them and the Steelers at 10-6 with Cincy having only 1 division loss where as the Steelers would have had at least 2.
Just for the sake of 'covering the bases', even if they lose to Pittsburgh in week 2, I think the 2 point loss vs Houston in Week 16 where Hill and Burkhead combined for 50 yards would be another game where I think Elliott could have been the difference maker.
Of course, if Elliott got suspended for 6 games, so maybe they don't make the playoffs last year. Making the playoffs the year before would have given them a completely different mindset going into last season, so anything could've happened... even them only winning 4 games. My guess though is that double digits would have been more likely.
This is all academic of course, but I'm simply basing my assumptions how what we saw in Dallas over the last 2 years... where we saw how awful the Cowboys were in the 6 games Elliott missed, and the other 26 he played. As well as the mediocre play of the Cincinnati backfield over the last 2 seasons.