With Kyle, so much of what he was doing came easy and natural to me because I was basically already doing 60% of what he does and was already coming to a lot of same conclusions and preferences after years of training. Also being out of training for about 4 months with my recent illness (the longest I've been out of training in 5 years) really gave me some perspective on what training means to me, why I'm doing it, and how I want to do it. Someone else may look at what Kyle does and absolutely hate it or at least think that they personally would hate doing it, wouldn't work for them, whatever. The best part about the body and about training, if that there's absolutely no reason to do something you don't want to do or that you know doesn't work for you, specifically.
Training (and nutrition) is very tricky because you can't just be totally clueless and do whatever you want and expect results, but at the same time, once you have a foundational set of knowledge about training and your own body, you sorta need to throw out the conventional rulebook and rebuild everything according to no one else but yourself, while still utilizing the advice and suggestions and hard-won experience and lessons of others. So yeah...it's tricky.
Kyle's is definitely not saying just do push-ups and pull-ups and you're done. He does a good variety of exercises, but he also does a lot of variations and progressions of the same exercise. He doesn't do the same variation in back-to-back days. His overall goal is also not traditional bodybuilding and hypertrophy at all costs, but he is still very interested in aesthetics, which I love about his approach (Greek statue body). According to my overall understanding of his program, he does 3-4 different main exercises a day. These are exercises that he is trying to optimize to complete a minimum of 10-20 sets of every single week. Basically how many reps can you do of pull-ups and still complete 10-20 sets of them every week? This is all about your personal max. If your failure set is 12 reps, then you'd probably want 10 reps per set. But then you have to think if you can do 10 sets of 10 reps in a single week. You have to find what your limit is. 10 sets of 10 reps a week might be super easy for you, so even if your failure set is still 12 reps, you'd want to up the weekly sets to 15 or whatever. You need to do the same for all of your main exercises. Only you can find the answer since it's based on your body and where you are right now.
Failure is pretty easy to understand:
1. The complete breakdown of form - if your push-up doesn't look like a measured, solid, proper push-up, you're at failure.
2. Inability to continue. If you literally can't move anymore, you've hit failure.
Knowing when you are close to failure is all about mental focus and mind-muscle coordination. His program is not great for beginners because they likely haven't developed this much at all yet. But even for intermediate - advanced, you can't expect to have great mind-muscle coordination the first time you do a new exercise. Kyle focuses very heavily on mental focus and rock solid form. I love this about his approach. Then you can add pauses and holds to your form to make it ever harder.
I'm doing alternating Pull / Push days for upper body days. If I did push last time, I do pull this time. I may use the same exercise, or I may not, but I never use the same variation back-to-back. I'm still finding exactly what variations give me the best results, and I'll likely have to change them up after awhile anyway. Most exercises are bodyweight / calisthenics / bar work / ring work, but I also use dumbells and resistance bands. So far I don't use any cable / weight machines, or barbells.
I focus 60% on upper body because that's what my body needs. Someone else may not need this and will prefer more legs days or something. With my variation day I'm experimenting with different things like horse stance, super-sets, burpees, farmer's carry etc. I just plan out 3-4 exercises in my head and do them. I do abs with my leg days and on my variation day.