I wonder about this:
Ive always used straight sets, for example 4x6, same weight. when im able to complete all 6 reps in all 4 sets then I increase weight next workout. but if I do 6 reps each set then probably I could have done sth like 2 more reps in 1st set and 1 rep more in 2nd and 3rd set. is that ok? or this is counter-productive to have 2 reps in a tank at the end of 1st set?