Been tandeming for over 33 years.
Have ridden as high as 9,200 elevation. Have done long/fast/ twisty descents. Have done 50+ mph on less twisty descents..
All with only rim brakes.
Have used centerpulls, U-brake, V-brakes, cantis at one time or another on our tandems; been able to stop as needed.
Have test ridden discs and have used drum . . . both are fine but we stick with rim brakes cause they work just fine for us.
Just our experience.
Pedal on TWOgether!
Rudy and Kay/zonatandem