The game assumes the players are fully bought into the premise. You are basically a strike team that works for The Envoy. You don't begin the with players just realizing who and what they are. You assume that's already happened and they have accepted who they are and what they must do. So they stay together because The Envoy has assigned them to be together.

To that end the game heavily implies that Shadow do tend to be big fish. These are power players already with high stakes, high ambitions and therefore high emotions for the Shadow to become addicted to. A lot of the example Shadows in the book are things like Revolution Leaning Union Leaders and Foremen of Entire Mining Operations. Some of them are a little more low level, like a Serial Killer or something but even then they are presented as people with means and resources that require a team to overcome.

There are no classes. There is something a kin to "races". In addition to playing humans you can play genetically engineered "uplifted" alien species and A.I. driven robots of sufficiently complex intelligence. Basically these things have developed intelligence capacity as to be compatible with Numina melding.