This is a late reply but since I start my new timetable on Monday I was looking for any helpful stuff- glad a thread has been made already! The reason it is out of 100 is because the exam will be scaled back so much (For National 5 it was like 2/3) and then they add the assignment mark- which is out of 30 I think. I too did old higher, but I bought a new higher textbook and during the summer I will learn the relevant stuff that I missed out on in CfE Higher
EDIT: I remember seeing some of the stuff I missed out on in CfE higher in some old Advanced Higher notes, so they may be useful as well