They don't have to literally related with said powers, Luffy's power aint fire, therefore Forest God doesn't necessary = Ryokugyu's power, it makes sense but Luffy aint fire, unless Sabo at some point gets called Sun God from Flame Emperor but I doubt. Probably more symbolic rather than literally
Sungod - Nika (a devil fruit, Luffy so far)
Rain God - Shiryu's weapon, or Imu raining destruction?
Earth God - no clue, something red line related? Blackbeard?
Forest God - perhaps the Yggdrasil Tree inspiration located in Elbaf?