I find that rep ranges depends on the exercises. Squats and Deadlifts are, in my opinion, best done at low reps. Bench Press can be done at low reps or sets of 8-12 reps. Nearly all assistance work is best done with sets of 8-12 reps.
THIS ^^Low-moderate-high Rep ranges all have their place... just be sure to figure out for yourself which one stimulates your muscle the best (and that depends also upon which exercise your doing). Just to be safe, I would say you should at least do one heavy compound movement (e.g. dead,squat,bench) to absolute failure for 5 reps or less for tGlut activation.