This makes them more maneuverable, a key element in freestyle canoeing. The rounded arch hull also sits deeper in the water when not leaned, giving it good lateral resistance and acting like a keel to help maintain course. I won't say much about materials. This is an involved subject and is better left to longer references. Suffice it to say that, for quietwater, I believe you should generally buy the lightest canoe you can afford.
Trim work is another subject altogether.
Wood gunwales are aesthetically pleasing but require extra maintenance. And sliding bow seats may be more expensive but they give you added control of fore and aft balance. Test paddle everything in the kind of water you expect to paddle, carrying the kind of loads you expect to carry. That way you'll know if the boat handles the way you want it to.