Mixed

Resistance training produces comparable muscle hypertrophy across a wide spectrum of loading zones (heavy, moderate, and light loads) provided sets are performed to or near muscular failure.

You do not need to stick to a specific rep range like 8-12 to build muscle. You can use heavy weights (fewer reps) or light weights (more reps) as long as you perform your sets close to failure. Moderate loads (9-15 reps) are recommended as a practical default because they are time-efficient and easier on your joints, but varying your load can be beneficial.