Yes, I do not think that these departments have a lot of misconduct at all, and I think that the people that are in them do a good job and that they do not cause any trouble for the system or in the way that the government is working now.
An Internal Affairs department is a good sign that a department is serious about minimizing misconduct, however, it is not a guarantee. In any organization, there is the possibility that a mentality could develop that steers individuals to overlook misconduct in order to protect the institution and avoid making waves. An Internal Affairs unit would not be immune from this.
It has been claimed that police often operate on a buddy system, in which officers protect one another from consequences. Internal Affairs representatives are often retired officers or officials who know the politics of a particular office. Therefore, having an Internal Affairs does not cancel out the buddy system. Additionally, an Internal Affairs department is likely more focused on major cases that affect the image of a department. As well,not all police misconduct is reported.
I think whoever is in charge of a police department determines whether there is a minimal level of police misconduct. This isn't to say that an Internal Affairs unit doesn't help, but even within these small groups, there is the shading of truth and misconduct of their own. Viscous cycle.
No, the existence of an Internal Affairs unit does not guarantee that departments have the minimum level of police misconduct, because the fact that there is even a police department to begin with guarantees that there will be police misconduct. Humans are humans, and they will do bad things, whether they are investigated or not.