It’s very difficult to give a general number, since everybody is different and it depends on stuff like you muscle fiber dominance (which only you can know), but around ~80% of your Rep Max. should be ok.
(So if the program demands 3 sets of 10 reps for several exercises after each other, chose a weight with which you can perform said exercise for 12 good reps)
Be sure to experiment though ! Try to increase the weight each time you can complete the 10th rep on the last set with good form
Wow that’s going to be pretty brutal…the deads are gonna be killer after squats with no break and at 80% RM. Have you done this circuit before? If so, how much time between each circuit? how long does the entire workout take? and is it reasonable to expect to be able to do some Plyometric work afterwards, as well as some cardio?
Not the exact program, but this type of circuit training is very effective, and thus very common among athletes, not so much traditional ‘Bodybuilding’, but people who do wrestling (or any other any kind of martial art), rowing, police/military forces etc train like that all the time.
Compared to a traditional ‘Bodybuilder’, those people have less maximal strength (because they dont need it) and more strenght-endurance/lactate acid tolerance and cardiovascular endurance. So 80% was an estimate, if you are new and not used to that kind of stimulus or maybe just very strong/fast twitch dominant, then 80% might be to high for you. Its impossible to give an exact number, if you start with your 12 rep max weight and can only do 7-8 reps on the third circuit, than you have to lower it (obviously). Just try it out once
During the first circuit (4 exercises if my memory serves me right), you are not supposed to rest in between. Rushing from one exercise to the next and positioning yourself etc will give you ~5-10 seconds or so of ‘rest’. After completing the circuit once, rest for ~120 seconds before starting the new round. The second circuit has 2 exercise and you are allowed to rest for 60 seconds after each round
This kind of workout is complete different league than your typical Bench-Curl-Situp session, so be prepared, bring LOTS of water to drink (2l+), bring a towel, look out for the next bucket/ect if you have to vomit (not joking). Do not eat right before (leave ~1 hour between your last big meal and the workout), warm up properly, stop immediately (!!) if you start feeling a headache/feel dizzy etc
Some light cardio may be possible, but there is no way you can do any kind of plyo…