Some of the GL transitions work well, not all. Cube, Doorway, and Grid Flip work well.
The GL transitions work best with either an overlap transition, or using two tracks with an opacity filter. They used to work well with Mask From File, but there have been so many changes and enhancements made that they don’t work very well anymore.
The page curl transition never worked very well.
To make a decent page curl you need to use green screen footage.
I used two projects for this. The first is used to key out the black and add the images. Then created a second project, added the first project as MLT, added the images and video, keyed out the green.
If you want to use the page curl clip, It is on Google drive.