Touring boats have two requirements, they need to have room for gear, and they need to be able to cover distance efficiently. Room to carry gear is primarily a function of boat volume, to more volume, the more room to carry gear. The volume needs to be configured so it is relatively easy to load and it needs to be distributed such that a heavy load will not cause the boat to bog down.
If you intend to travel long distances in your boat, it is important that the design can carry the load efficiently. There is a difference between being fast and being efficient, but they are related. Efficiency means that you will go the farthest distance with the least effort. Fast means that for a given effort you will go faster. Efficiency is related to speed in that when you put your time and effort in to moving the boat, you will go farther by going faster.
Almost all the my sea kayak designs will work for trips of a couple days, but some of them are well suited for multi-day trips. These boats have the combination of volume and efficiency to work well on longer trips.
The Expedition Single is my premier design for touring. It has a higher back deck for easy loading of gear, plus it moves easily and efficiently through the water. It stays responsive and easy to handle even with a good load.
The Great Auk is a good all around boat that is stable, comfortable and efficient and has plenty of room for gear.
The Razor Billed Auk was designed as a recreational racing design, but due to its volume and efficiency, it will serve as a good touring boat.
For those who plan on heading out sea for a truly extended trip where the ability to carry the kitchen sink may come in handy, take a look at the High Capacity Great Auk. It has the capacity for just about anything.