About the Billows, I'm reading the top vent has to be closed 1/4 to 1/2 for it operate effectively .... is this true
Yeah, that's what they tell you. But it is not the idea way in my opinion.
I built a flow gate into my Billows to limit or control the amount of air involved without closing off the top vent. I did this to insure clean smoke. Throttling the top vent on a WSM does not promote clean smoke in my experience. Running about a 1/3 open on the blower and the top vent wide open gives me excellent control with Thin Blue Smoke...
That said, I'm cooking with my Masterbuilt 560 exclusively since it's purchase simply because its fun, easy, and gives good results. Temp control on the WSM is better but the MB is good once it is stable. I do use the Signals for monitoring the temp since the MB app is garbage.
We did St. Louis Memphis style dry ribs for the 4th. My wife and I think they were the best ribs we've ever had, commerical or otherwise. Certainly the best I've made.