Regarding burning only wood in the WSM, I have tried that in my never-ending search for perfect BBQ--or at least to place in the money.
What I did was use a neighbors portable fireplace (those things are big in the midwest) to build a fire out of logs and branches of apple wood. As the wood turned to coals, I added it to the WSM as needed to maintain the heat at 225 or so.
My results and conclusions--it is not worth the effort. Results were ok, but, the additional work did not produce additional quality. I tried it with pork butt--most forgiving meat around in my opinion. Flavor was as good as always without being too smokey or bitter--but, I had to check the temp every 30 minutes the entire cook. This was before I got my first remote thermometer.
I like the idea of using wood coals--and I still do that to light my charcoal sometimes--a hybrid between the Minion method and using wood. I take 3 or 4 chunks of wood and light them in my chimney or even my little Smokey Joe Weber Baby Kettle and when they get to coals, I put them on top of the charcoal. I only do this when I am cooking purely for fun and have extra time to get the fire going. Not sure if it really makes that big of a difference-but, it feels right, so I do it on occassion.
Regarding the Minion method, Jim is humble beyond description as I know only a few WSM owners that don't use it regularly for cooking. He, and Chris, and Stogie, and a couple others on this list have had a profound impact on the cooking habits of all of us--to the better I might add.
Dale