If Chelsea can stop PSG from scoring early goal or even scoring in the first half, then they might have a chance of winning the trophy. If they fail and PSG happens to get an early goal like they did with Real Madrid, then Chelsea might suffer a terrible defeat just like what happened to Inter Milan in the last champions league final when they played PSG. The match may not even be as tough as the semi final match between PSG and Real Madrid.
In recent times, it has become very difficult for opposing teams to stop PSG's attacking players. Even Inter Milan's strong defense could not stop their strikers in last season's UCL final and Real Madrid's defense could not stop their attacking part in the last match. PSG's attacking part has been a headache and threat for the opponent many times in big matches. Now let's see what medicine Chelsea take as an antidote to this headache. It is also worth watching how they take action against this threat from PSG.
If you check well, most of PSG goals, in the matches they won with big margin, came in the first half which means that is the time any team that want to stop them should focus on defending and preventing them from scoring. When their strength and stamina might have reduced from second half, then the match becomes balanced and open for either of the sides to win. This is just the point I'm making and if Chelsea should use this strategy, they might have hope of winning.
I agree with you if Chelsea can stop PSG from scoring an early goal in the final or even scoring in the first half, Chelsea might have a chance of winning the Club World Cup, but I think Chelsea shouldn't only do that if they want to win the Club World Cup; they should also be the first to score a goal in the final. If Chelsea can do these two things against PSG in the final, they are one step closer to winning the Club World Cup, but if they fail, PSG will likely beat Chelsea with so many goals.