When using your WSM you have to remember that it's not designed to be constantly puffing smoke. If it was then you wouldn't be able to eat the product.
As someone much smarter then I pointed out a while ago... smoke isn't "absorbed" by the meat but rather "adsorbed", meaning its the build up on the particulate on the outside surface of the meat. Whether you add 5 chunks at the start or stagger them over the cook (assuming consistent heat), the result should largely remain the same.
If you are going for show then go ahead and spread out your chunks. If you want a good smoke ring though (purely appearance) then you will might want to add 50% or so at the start.
As for "light smoke" flavour, I would reccomend looking at using largely fruit wood (cherry, apple, etc) and only 1/2 chunk of hickory. Assuming fist size chunks I would say 3 chunks apple, 1/2 chunk hickory. If you want a stonger smoke in the future you can look at bumping up to 1-2 chunks of hickory and keeping the fruit wood the same.