Okay so going by size of Faerun, which is not the largest continent on Toril, Toril has to be a Super Earth to fit so many enormous Continents and Oceans.
Some have asked how can so many races, species of Dragons, ect..., in a setting. In this case Toril is likely a super earth (low end of the super earth scale). And that is alot of space for stuff. And that is before you concider Toril's mirror planes, sister planet Abeir, the rest of its solar system, or visitors from other worlds and other planes.
Super-Earth - Wikipedia
en.m.wikipedia.org
Some have asked how can so many races, species of Dragons, ect..., in a setting. In this case Toril is likely a super earth (low end of the super earth scale). And that is alot of space for stuff. And that is before you concider Toril's mirror planes, sister planet Abeir, the rest of its solar system, or visitors from other worlds and other planes.