Circuit Playouts go beyond just moving from one exercise to the other and moving as quickly as possible. The ability to train the body through different tempos and form is a top quality to acquire but at the same time, it's critically important to be aware of breathing and the speed to push through with the best intentions. It challenges your conditioning but it also challenges how you breathe and move throughout a single circuit to multiple rounds.
I have mostly done circuits in the 6-9 range of exercises and do my best to get in 5-10 rounds depending on my mood, the shape i'm in at the time and the difficulty the exercises are. If you're an athlete training for a sport say like MMA, Wrestling, Football, Hockey; you want to be able to move as quickly as possible with limited rest periods between circuits and be able to withstand even great stress. What this teaches is that if you can push through a tough circuit multiple times with very little rest, you can handle extremely well in a competitive environment. However, not all of us can have that luxury because for the average person, pushing that hard can lead to many physical problems and your oxygen levels become more depleted than accustomed to over time.
I believe circuit training can be very beneficial but for the sake of health purposes and a goal to build up strength & endurance over time, its important to focus on the 3 main factors to take on high levels of conditioning; breath control, muscular control (solid form) & tempo. If you move too fast too quickly, your body will shut down in a negative way and you'll need more time to recover, if you move too slow or the playout isn't quite right or not enough you won't make the progress you want. It's like the Goldilocks & The Three Bears concept, there's too much, not enough and there's that one that fits you perfectly. This is where experimentation and focus on how your body operates and is leveled to a particular easy or advanced playout.
Everyone is different so build up to what works best for you and adjust according to your level. On some days it's good to back off and do lesser rounds but on your energetic days you can go for as many as 10-20 rounds if you wish. I also believe in how your energy plays out in this type of training. Pushing to the absolute limit can really deplete your energy levels and you won't be boosting hormones at a great rate; matter of fact your hormones and testosterone levels can drop if you do too much. When your energy levels are leveled to where you can be energized during and after a circuit playout can have a great deal of benefits when done correctly. Circuits can be a powerful way to surge growth hormone, testosterone, strength endurance & energetic properties that lead to greater recovery and accumulate amazing muscle definition & natural muscle mass. It wouldn't matter if its weight lifting, bodyweight, cables or whatever; if you can use the energy to your advantage and use the right form of leverage to where you can be as strong going in as you are coming out of it you're still having a great deal of power throughout your circuit training.
Bodyweight circuits are the best in my opinion because not only can you do them practically anywhere but you learn the sensitivity at a greater rate of your body moves freely than by moving weights because with weights eventually you're moving with the weight instead of moving freely on your own. Be simplistic using pushing, squatting, ab play and some grip to get the most out of your training. You can supplement other exercises but stay with the fundamentals and you'll never go wrong.