Yep. Leverkusen performed perfectly, they win all the matches in the group stage. No other teams could win all the matches, including Liverpool and Roma. In the early competition, we hope Liverpool and Roma will perform well as Leverkusen, but they seem not in their best form. So, we can assume that Leverkusen is the most favorite team to win this competition because they look to play consistently until the end of this competition.
Leverkusen and Liverpool will not have to play two play-off matches but AS Roma will have to join play-off with a club drops out from Champions League. They finally got a big win against Sheriff but it was too late and they only ended their group at the second position.
We have to wait till play-off round ends before discussing more about best candidates for the winner of Europa League in this season. Even it is too soon but it is better to start discussions about it when we know about all clubs that will participate in Europa League knock out phase.
Leverkusen and Liverpool look to be strong and best candidates for this race but a general picture can be changed when some big clubs from Champions League join Europa League.
In general, clubs from the Champions League who join the Europa League are not as strong as Liverpool and Leverkusen, but the presence of these clubs can be a threat to them. I only consider Milan, Lens and Galatasaray who can pose a threat, but based on the consistent performances of Liverpool and Leverkusen, the presence of these clubs can improve their quality to go further in the Europa League.
The results depend on the end of the play-off round, after which a new round will begin. The more strong clubs that join the Europa League, the more excitement there will be for the audience when strong teams compete.