Imagine that you were only allowed one chart (or board) at the gemba. What would you pick? What is the Swiss Army knife (I'm more of a Leatherman Multitool fan myself) of charts that gives you insight into process adherence and process performance?
One of kaizen's unofficial taglines is, "Just do it." And it makes sense. We try to spin the PDCA wheel as fast and as frequently as possible in order to experiment and quickly learn and make adjustments.
The best intentioned try to apply PDCA as well as SDCA (standardize-do-check-act), but often fall far short on the check side. Of course, this means that the likelihood they will act/adjust appropriately is slim.