The level of detail that a project manager should be involved in a project should not be static. As the project progresses the amount of oversight needed fluctuates and the project manager needs to adapt if they want to make best use of the resources available. For a project manager who does manage at one detail level you have two extremes. Managing from Far
The first is the project manager who always manages from very far and with very little direction. This can lead to a project going way off plan and a lot of finger pointing when problems arise. The project team will also think you do not do anything and have no respect for you. More so if they see the project manager taking two hour lunches.
Managing to Detail
On the other spectrum is the project manager that is involved in every single little detail and will even go so far as to act as the subject matter expert on every project deliverable. This approach can suffocate a project team and gives the impression that you do not trust them. You will end up finding a project team that does not want to work very hard for you. It also takes up all the time of that project manager, making the person either only able to handle one project or work long hours.
Manage Dynamically to the Situation
I find the best way to manage is dynamically. The project manager should step back when they see that everything is on track and zoom in when they notice potential risk around the scope, cost, or schedule of the project. Another important time to zoom in is when the project is nearing a major milestone like an implementation. Not only does this build trust with the team, but they see that the project manager will swoop in to help when needed. This will maximize your time so you can run multiple projects effectively.