1)
Who are the great kings?
1.
Rashi (from Yalkut Mechiri): This hints to the 31 kings [of Eretz Yisrael]. Pharaoh and his army (verse 15) are equated to them 1 . And striking Egypt is equated to awesome kings stronger than them (the 31) - Sichon is [equated to] all 31 [and also Og is like all 31] - "l'Sichon Melech ha'Emori ul'Og Melech ha'Bashan ul'Chol Mamlechos Kena'an" (135:11).
2.
Radak: They are the ones detailed below (Sichon and Og - verses 19-20). First they are mentioned as a Klal, to increase the praise [that Hashem struck them].
1
I.e. one verse teaches about Pharaoh and his army, and one (our) verse teaches about the 31 kings. (PF)
