At the rear you need a bracket brazed to the seatstays, or suspended from the seatclampbolt. On modern frames destined for V-brakes retrofitting this part could prove difficult. Classic-style cantilevers are rather wide, and are known to poke holes in bags. Depending on the geometry of your feet and frame, hitting them with your feet is another option. Low-profile cantilevers do protrude a lot less, but are less efficient and need more cabletravel.
Most cantilevers use post-type brakeblocks which are fiddly to set up.
Modern designs use brakepads with a single bolt and conical washers, which are a lot more convenient. The parallelogram action is nice on paper, but for a touring bike fewer moving parts is to be preferred. Bolt and washer type pads are much easier to setup. Using a V-brake on a bike with dropped handlebars is possible, with some ingenuity. The braided cable follows a tortuous route and relies on a kink to stay in place, and reports have been made of cables breaking.