I have one disc brake, that is on my Lynskey rear. And a V brake with Koolstop Salmon pads on the front of that bike. The disc unit is a Spyre, they recommended compressionless brake cable, that I bought and used for the install.

On that bike I wanted better braking on the disc, switched to a cheap resin brake pad to get that better braking. With that modification, the front and rear brakes work roughly equally well in dry conditions. Wet conditions, the disc works better after a few wheel revolutions wipes the water off the disc. But with the resin pad, the disc will fade after about a drop of 400 feet on a steep decline, the V brake does not fade on that hill like the disc does.

On that Lynskey, I found out the hard way that the front V brake is too good. Some moron in the left lane suddenly decided that they wanted to change to the right lane to make a very sudden panic stop, I was in that right lane and had to jump on the brakes hard, went over the handlebars. Had a sore rib for several weeks, one brake cable adjuster hit something and broke, otherwise no real damage. Three cars stopped to see if I needed an ambulance, but nobody got the license plate number off the car. I doubt if any disc brake would have done any better.

My other bikes with V brakes or canti brakes are fully adequate at stopping.

I have never ridden a tandem, can't make any comparisons with a drag brake based on experience. But the beefy drum brakes that I have seen on older tandems clearly looked like they were a lot more capable than the little drum brakes I have seen on solo bicycles like my 1960s vintage utility bike.

Quite frankly the side mounted drum brakes I have seen on Tandems looked more capable than the rear drum brake that was bolted onto the side of the hub on my vintage Triumph motorcycles, but those Triumph drum brakes always performed great.