Disclosure : I haven’t used Prepladder, except for the free videos, this answer is my thoughts and my friend’s opinions who have used prepladder.
It’s always the best to do the main videos, at least subject’s like Gynecology, Medicine, Surgery, PSM, Pathology and Forensic Medicine. Why? Because these subjects carry about 160 marks, which will take you over the line.
For subjects like Derma, Anesthesiology, Radiology, and Psychiatry you can do rapid revision videos as more or less you can save time and even with knowledge from other subjects you can answer the questions.
For rest of the subjects, it depends on your time and interest, but preferably do the main videos. Best wishes.