olympic lifters generally (as far as I know from my friend on the oly team @ FDU) never go over 6 reps in training, and thats usually for some form of squats or overhead press’s.
You’ll see powerlifters doing tons of different rep schemes. Max effort work is usually 1-3 reps, Dynamic as well. Repetition work can be from 3-15 or so.
As for isolation movements, for powerlifters, pre-habilitation work generally will be isolation, like tricep pushdowns, front/side/rear raises for shoulders, plate curls for hamstrings.
I know my olympic lifter friend does Russian Arm Bends (aka curls) so that his triceps don’t overpower his biceps and tear his elbow off.
note : this is my view on it, and nothing more.