The Superhero Database Classification number, or SHDB Class, is a number that represents the overall 'power' of a character. All traits of a character are used for calculating the Classification.
What it DOESN'T mean
This doesn't mean that a higher class would always beat a lower class character. But the bigger the difference in Class is, the more obvious it is who'll win in a fight.
How is this calculated
( INT^1.3 + (STR*0.5 )^2 + (SPE*0.5)^2 + DUR^1.6 + (POW + (SPS*SPL))^2 + COM^1.8 ) ^ TIER
Super Power Score and Level
Every Super Power has a score (SPS) that is used to calculate the Class. Each Super Power also has 3 levels (SPL). The level is set when connecting that Super Power to a character. The level determines the final score, of the Super Power, being used in the calculation.
Once they're invincible, the team FF has plenty of methods to win.
Vaan could easily summon Zodiark whose ( -> Final Eclipse seems to cause Big Bang levels of Attack Power, or they can spam limit breaks etc . Team FF wins.
Why would I wanna do that ?
Other people aren't gonna learn more about the entire Final Franchise (which has been around for more than 35+ years, with so many game titles (most of them in separate universes / multiverses, yet still all of them are unified e.g. in the Dissidia Umbrella. You can easily imagine that the FF Mega-Verse completely dwarves SCP (thanks to the sheer enormous quantity of FF games / spin-offs & worlds where all of those games take place)).
Some FF games like esp. FF3, FF5, FF13, Ivalice (FF12), FF8 are already at least (High) Complex or Hyperdimensional Multiverses by themselves, and now guess what you get when you stack all of them together into an even bigger multiversal structure (e.g. Dissidia) !?
Obviously SCP cannot possibly hope to compete with 35+ years of Final Fantasy Canon. Final Fantasy is just way bigger.
Even the two big Comic Franchises (DC Marvel) cannot easily be proven to have produced even more content and therefore an even bigger multiverse than what Square Enix did with FF.