Robert Haddad, a Catholic apologist from Australia, just uploaded a video where he not only argues for differing levels of reward in heaven, there are different levels of glory therein:
Are there different levels of glory in Heaven?
Haddad seems to believe that “third
heaven” (2 Cor 12:2) is to be understood as a third level of heaven itself, and
should not be understood as some want it desperately to mean (i.e., “first
heaven” being the sky and “second heaven” as the stars/universe”).
Further Reading
Paul and the "third heaven" in 2 Corinthians 12:2
Paul's vision in 2 Corinthians 12 and Apocalyptic Eschatology
Early Christians and 1 Corinthians 15:40-42
Possible Origenic Homily and the "third heaven"
"Third Heaven" in 2 Enoch and the Apocalypse of Moses
Jonathan T. Pennington on the Development of Multiple Heavens in the New Testament Era
The "Mormon" interpretation of Matthew 13:8/Mark 4:20 in Fragments of Papias
