I not saying that Nagato will always solo Itachi with Deva and Animal Path. I'm saying he can potientially beat Itachi with just those two.
Deva Path
-Would force Itachi to keep Susanoo active/ready to avoid great damage. However,Susanoo is only a temporary defense.
-Deva Path would deflect all of Itachi's attacks
-Deva Path can get rid of amaterasu
Animal Path
-Will give Nagato a greater field of vision
-Can use the drill-beaked bird to fly
-The other summons would keep Itachi on the move, forcing him to use up chakra to get rid of them
-Itachi can only get rid of the cereburus/dog by using amatersu
-Itachi would forced to rely on amaterasu to hit Nagato when he's flying on the bird
With just these two paths, Nagato would be safe from Tsukyomi and would force Itachi to wear himself out.
Deva Path
-Would force Itachi to keep Susanoo active/ready to avoid great damage. However,Susanoo is only a temporary defense.
-Deva Path would deflect all of Itachi's attacks
-Deva Path can get rid of amaterasu
Animal Path
-Will give Nagato a greater field of vision
-Can use the drill-beaked bird to fly
-The other summons would keep Itachi on the move, forcing him to use up chakra to get rid of them
-Itachi can only get rid of the cereburus/dog by using amatersu
-Itachi would forced to rely on amaterasu to hit Nagato when he's flying on the bird
With just these two paths, Nagato would be safe from Tsukyomi and would force Itachi to wear himself out.