Yes. And is studying more, or less efficient, when lectures are spent focused on transcription, instead of the material?

In lectures, focus on the material. When working from the book, you have oodles of time to transcribe. Hence, both modes of learning.

For some lectures I follow the course in class. For some other lectures I just read the slides on which the lectures are based and go in depth on my own. Some other friends follow all the lectures. Some others just don't follow that much.

I don't know why you provide a one method that should fit everyone, while everyone has a preferred way of studying that isn't necessarily the best approach for other people

Because the lecturing professor assigned a textbook, making both lectures and the textbook relevant to the course.

Also, it's at least three distinct methods! Read before lectures, read after lectures, read on both sides. Dealer's choice. Neglects recorded lectures and the possibilities they open up.

Talking about people's preferences and studying is funny. Most people prefer not to study. Preferences have little to do with good study habits. The above approaches have worked for hundreds of years just fine.

Well, of course if a textbook is required to be read, you read it period. I was talking about different study methods in the bounds of what is allowed to do