Doing a heavy set followed by lighter ones without resting can help you do more reps with light weights, just like doing only light curls.

You can get stronger, bigger, and more enduring muscles by doing one tough set followed by lighter ones without resting—faster than doing multiple heavy or light sets.

Doing a heavy set of arm curls followed by lighter ones without resting can make you stronger in one-rep max and static strength, just like doing only heavy curls.

Doing a tough set of arm curls followed by lighter sets without resting can make your biceps grow just as much as doing only heavy or only light curls over 8 weeks.

Doing one heavy set plus lighter ones without resting takes less time than doing three full sets of heavy or light curls.

Doing light weight exercises until you can't do any more for 8 weeks won't make your arms stronger or more powerful if you're new to lifting — you probably need to lift heavier or move faster to see real gains.