The difference between an Avataro Change and a Gokai Change is that the Donbrothers still keep their belts, similar to Kamen Rider Decade when he transforms into other Kamen Riders. It is unknown if using a single Avataro Gear will transform the Donbrothers into the full team or just a specific hero of said team.
Finally, the show's monster of the week are humans turned monsters. The first monster they will face is Kishiryuki, an Oni that is said to be inspired by Kishiryu Sentai Ryusoulger.
[Source: HeroShock]