The add-on will create a collection called Page Collection. Look for the object "Controller-Object" listed within this collection. You can easily move or rotate this controller object - the entire book will also move or rotate accordingly. And the interesting thing is, the pages will still flip correctly in their new positions.

The pictures must be named sequentially starting with 1. So they have to be named as 1.jpg, 2.jpg, 3.jpg etc. or 1.png, 2.png, 3.png etc. If they have any other names, the add-on will fail to detect them correctly. Also, do ensure that you select the correct folder as well. If you are using video clips, please have them named like 1.mp4, 2.mp4, 3.mp4 etc.

The video clips are played at the same fps as that of your original animation. To slow down the speed or to make it faster, go to the output settings in Blender and change the frame rate as appropriate. The video clips will follow that same rate.

Yes, you can use still pictures for some pages and video clips for the other pages. For example, for a video flip book, the cover page may contain only a still picture. The same is true for any other page. Just name your pictures or video clips accordingly. If you keep 1.jpg, then 2.mp4, 3.mp4 etc. in the source folder, the first page or the cover page with show a still picture and the rest of the pages will display the respective video clip.