The Kayak is a means to move you from one location to another. Just as hiking (backpacking), automobile, an ATV, mountain bike, horse, et cetera, are ways to move you and carry your stuff.
The interior available space within many kayaks is greater that the average 60 liter backpack that people use for multiple days in the woods. The type of kayak you should look at would be one that has two or three bulkheads one in the bow and one or two in the stern. Having a closed storage in the front and rear of the kayak will also add buoyancy to the kayak in the event of it capsizing.
Another good option is the sit on top kayak. There is so much space in that boat it is crazy. You just need to use small dry bags that have labeled long ropes attached in case they move around. This way you will not strain your back trying to look for gear.
If a stand up paddle board is more your style then think like a trail runner or day hiker. You will be putting lightweight items into small dry bags in front and behind you.
It is all about making choices of balancing your skill, taste, budget, and comfort at night. To camp from your kayak or stand up paddle board watch one of our YouTube videos (coming soon) and register for our next intro to Kayak/SUP Camping class.