You see, this is where you and I conflict and you never comprehend.
Your comment "Depends on the weight" is a common misconception of exercise.
The weight you use must be heavy enough to force fatigue, to stimulate growth.
The rep ranges one uses will determine the weight on the bar, the number of rep's used will determine the degree of stimulation, but the most common sweet spot for muscle growth is 10 reps.
Based on a controlled speed of 2/4/1
The general idea of 2/4/1 is that;
Moving (positive) 2 seconds from start to finish completely eliminates momentum, this ensures the the muscles are doing 100% of the work
Moving (negative) 4 seconds from start to finish has the same effect plus it enables the muscles worked to safely go into pre-stretch, which is key to strong flexible muscles.
Pausing for one second in the contracted position ensures you have complete control of the weight in your hand throughout the movement also the added benefit of strengthening the muscles much more efficiently.
** pausing (squeezing) is generally used with pulling movements, when pushing or squatting, the paused should short of using the limbs to support the load.
When one say "Depends on the weight", the only thing that's going to change are the amount of reps one can do, which is a good thing because of our fiber make-up (slow and fast twitch)
Do you understand where I'm coming from?
Adding really heavy weight and moving faster, in the negative has no benefit what so ever could even cause injury, moving lighter weight and just going through the motion is a waste of time.
Progression is key, using a controlled rep cadence and slowly increasing the two key components of rep number and weight over a period of time is the only way to improve your;
Strength
Flexibility
Muscular mass