Chelsea are clearly a class above and in much better form than Betis. Maybe the extra rest before this match will have some impact, but it will not be as significant as it might seem. The Conference League might not be the most prestigious tournament, but when you reach the final, you should not be asking yourself how important it is. If you have made it this far, you have to win and lift the trophy.
You're right that if Chelsea are already in the final, then Chelsea can make things change. The winning mentality when Chelsea are in the final, I think of Enzo and Cucurela. Enzo Fernadez is a young player who has experienced a final and the final Enzo has experienced is the World Cup. That's a good asset for Maresca.
Cucurela will also have the chance to be an unpredictable player for Real Betis despite not being a striker.
If Chelsea are able to win the trophy, I'm sure the Blues squad will have a positive impact on next season's achievements.