Like any other muscle group they should be trained through a wide variety of rep ranges.
Generally 12 to 20 sets of directed trap training will be enough for most people to grow according to Dr. Mike Israetel so most of your total training sets per week for trap training should be in that rep range.
The traps can handle very high loads such as in rack pulls or deadlifts and those exercises should make up most of your lower rep trap training.
Exercises like the barbell shrug and upright row are well-suited for moderate (8-15) rep ranges.
For the higher rep range spectrum, exercises like the dumbbell shrug are a good idea. With the higher rep ranges and lighter weight, it’s important to emphasize feeling the muscle work and focusing on the muscle you’re trying to target specifically.