We have an existing system in production, developed using a "chaotic" development process. I'm trying to introduce Scrum for all new development: new features, improvements, and bugs.
For new features, I believe the "As a <user>, I want <something> so that <goal>" user story template is the best option.
For bugs, "What I did", "What happened", "What I expected to happen" is the best format IMHO.
My question is: What format should I use for Product Backlog Items (PBIs) representing improvements to existing features? (edited for clarification)