Welcome to SMF!
I haven't had the pleasue of smoking Salmon myself (sounds great though), nor any experience with the Little or Big Chief Smokers. I know there a a few users of the Chief here, so someone with experience should be along soon. The only thing I know about them is what I've read, and fish or jerky is the extent of their limitations. I'm guessing the higher temps can't be reached due to the low output heating element, so ribs, butts, brisket, chickens, etc, would be a no-go.
As for adding smoke wood chips, as long as you can see or smell smoke coming out the vent, you're still smokin'. It will depend on the size of the smoker and chip pan, but typically a small handful will last for several hours in my small gas rig. Oh, I don't soak the smoke wood in water, either. Many manufacturers recommend thids, but I've found better ways to control the smoke by adjusing the amount of air and/or heat which they are exposed to. Sometimes placing the chips into a foil pouch will work, if not exposed to direct heat, of putting them into a seasoned tin can (burned out), then set it next to the heat source...if it smokes too much, just put the cut-out lid back on the can over the chips.