Welcome to the forum.
I will attempt to elaborate a bit without opening a can of worms.
Fuel type depends on the type of smoker, product being smoked, moist or dry environment in the smoker, whether you are hot or cold smoking, and most importantly, your taste.
If you are hot smoking in a smoker that produces a moist environment such as smokers with small vents or water pans, you will want to use a dry fuel. You are asking about chips or chunks so if a heavy smoke for a short period is desired, use chips, if a lighter smoke is desired for a longer period, use a single chunk. Start by using a two oz. chunk.
If your smoker produces a relatively dry environment. You may consider soaking your wood. This will produce a moist environment in the smoker which in turn allows the smoke to adhere to the product better than in a dry environment. The fuel type is the same as in the previous paragraph.
Experience will be your best teacher. Take good notes on your progress and experiment using different types of fuel.
Tom