Strength training is all about goals, about what you want to accomplish.
In a nutshell:
If you want to develop pure strength, ie: As much strength as possible with as little mass as possible, you keep the weight high, the reps low and the number of sets will depend on how many exercises you wanna do.
A typical "pure" strength protocol is the 6 sets of 3 reps or the 5, 4, 3, 2, 1 protocol ( 1 set of 5, 1 set f 4, 1 set of 3, etc, etc).
Then there is the protocol to build strength with some mass, like the 5X5
Then there are the mass building protocols like the 3 sets of 10 or the 10x10 german volume protocol.
The there are the ones that are focused on developing muscular endurance like the 4 x 16 or the 3 x 20, etc, etc
The point being that you need to be clear on what you want to develop first and train accordingly AND EAT accordingly.
Psalms 144:1
Praise be my Lord my Rock,
He trains my hands for war, my fingers for battle !