Do you have any numbers (even if they're rough) about how many graduate students accepted the offer this year?
Any advice would you give to those who will study next year? Do you have any textbooks to recommend studying before starting the program?
How hard are the courses? And the quality of lectures and research (from materials, lecturers, supervisors, etc.)?
I have no idea about any numbers for the 2024 intake, and honestly, I don't think worrying about numbers is sensible. Yes, admission is competitive, but not due to a limit of places, rather because the standards are high.
The program director will likely tell you after extending you an offer that you should prepare over the summer (and he will send some material). Do that, but please also remember to enjoy the summer! The terms at Cambridge are intense, so you don't want to arrive already feeling stressed.
The courses are at a similar level to my UG theoretical physics courses, so they are hard and require a decent commitment, but they are doable. The quality of lecture varies, as at each university. Some are great, some not so much.