Reading the OP's description of the new tandem it will be a disc brake bike. I am more than fine with rim brakes for a solo road bike. But when my wife was looking at a new solo bike in 2014-2015 I made sure that she got one with disc brakes. She mostly uses it for short trips to visit friends or go shopping. Disc brakes work better in the rain, and sometimes rain storms come in very fast here on the north plains.
My road bikes are all rim brakes. My MTBs are all disc brakes. Our tandem is disc. The only one that has had heat issues is the tandem, and that has been solved. For our bulk, MTB downhill brakes are, in my opinion, the best way to go. Lighter teams will probably have a different set of parameters, but even if my wife and I both got down to our ideal weight, we would be around 350 lbs. Add in the bike and gear for touring and we are in the 400 to 450 lbs. range.
Mine are Hope, SRAM, Formula, TRP, Trickstuff, and a whole lot more companies make very good downhill specific brakes. I prefer to use DoT 4 fluid because I know that I can get fluid anywhere that I am likely to travel without having to wait for it to be shipped to me. Others will prefer mineral oil fluids, used by companies such as Magura or Shimano. Drum drag brakes are mostly unavailable for new bikes. My setup as it sits today has been shown to work as both a drag brake to keep speeds below our tolerance level on descents, and as a fast stopper from high speeds.
If I am running my tires at the tire and rim manufacturer's upper limit for pressure (I do) and the PV=nRT thing pushes them up by 10 PSI I am running out of range. Probably safe, but not certified. I wouldn't want to have to stop on a steep downhill with a strong tailwind traveling 45 MPH with a rim brake bike.