I know that Jail machine relies heavily on Buffer Overflows, and Grandpa relies on pivoting.
Ippsec does a great job explaining both of these topics in his videos video about these machines on YouTube.
I think you should take the exam regardless whether you’ll pass it or not. If you pass it from first try then great. If not, then you have a very clear image about the exam and direction on how to prepare for the retake.
Wish you all the best.