I was recently involved in code reviews on a project. During the review activity, I came to the following levels of code review:
The lower you are, the better is the tool support for finding hot spots. Nevertheless, I fint it interesting to have this layering in mind when reviewing code. Depending on the layer, you have a different focus and the range of code you are looking at may vary as well.
This table may be not exhaustive, so I would be happy to get feedback on that.