No he didn't play at Mahomes or Jackson level.
Saying MVP level for Cousins is a serious insult at these two young QBs, let's not repeat that. Cousins played in the same level as Tannehill. Tannehill had same TD: INT ratio and similar passing yards per game in 10 games he played, with more rushing TDs than Cousins. Tannehill was also a "MVP candidate" in theory, but really they both weren't.
There were Only two exceptional QB performances from Patrick Mahomes and Lamar Jackson. (Then there was Derrick Henry among other positions).
Then there was quite a drop-off to other QBs. There were only 2 MVP candidates last year, and one became MVP candidate level in post season by winning the Super Bowl after MVP award was given to the regular season MVP.
Let's not insult what Lamar Jackson did last year. That was league haunting stuff. That's called MVP. Or how Mahomes came back from injury and won SB.