It's like everything else, a set of verified protocols that are best practice should be followed. Often we would like to have a standard list of,if this happens then I should do 1 2 3, and that probably works most of the time. Self defense scenarios and emergencies in general are dynamic and vey rarley happen when and how we think they will. It is better to have a set of plans than not but most times it is not so much what to do but when to do it. The timing of when and how to react can be more important than what to do.
Communication and preparation is the key to sucsess.
Do I try to shoot or apply a tourniquet at the same time as calling 911? No
When is it the best time to do so? When we make that decision.