If those two other cops were indeed such neophytes, the charges will likely not stick or be significantly reduced. But charging them can make it clear that not just the directly offending officer is responsible, but when you're on Team Blue, you have to make sure things stay safe and lawful.
I believe one newbie had policing experience at a school and as security guard at a mall or somesuch. Maybe nearly a decade of such security work. But yeah, Chauvin put them in a horrible position, was a police vet and their leader, and the one did reportedly suggest moderating the brutality, as per procedure.
I feel bad for them and they'll likely get off. Maybe Chauvin was actually showing off for these neophytes, indoctrinating them in the power and impunity of the police. In other words, the torture of Mr. Floyd might have been for the benefit of the two rooks, in Chauvin's twisted mind.
The Asian officer had nearly a decade of experience. I assume much of his defense will be that mostly he had his back to the knee-on-the-neck killing and was engaged in crowd control. One weakness in his argument is that the crowd was alerting him that the suspect was in pain, was being abused, couldn't breathe, was dying. But in a sense he allowed the senior officer to deal with the suspect, while he arguably did his job at crowd control.
Chauvin's going to jail and I'm glad they went with murder charges instead of manslaughter which is what such cases usually are prosecuted as (the few that get prosecuted). I don't know Minnesota's penal code, or if it's based on the Model Penal code or not, but generally the difference between 3rd degree murder and manslaughter isn't that much. The new charge of 2nd degree murder is indeed a level up.
I only saw less than 2 mins of the video recording the police killing of George Floyd. The two junior officers don't even appear. Though I think one taunts Floyd as not being such a tough guy anymore. And during that time, the Asian officer does crowd control and doesn't look at the intentional Chauvin violence.