Great questions. And thanks – i think this is the first question on the forum.
MBIs and story mapping first. Remember MBIs are about finding the smallest chunk of value that can be realized. Story mapping is a great tool for decomposing the MBIs I’d even say a little story mapping can be done during the selection of the MBIs.
MBIs and program epics. I’ll be candid. I hate epics. One must remember where they came from and when. In 99-01 there were quite a few of us doing Agile at the team level – Scrum and XP mostly. Both of these sprung from projects that were team oriented – that is, based on one team. The Agile Manifesto itself is still team centric. Epics were created by Mike Cohn a long times back where they really were just very large stories – but still pretty much driven by the product owner. Now we have business stakeholders -> product managers -> product owners -> teams. Trying to sequence epics has little value to me. Initial sorting of business capabilities and more defined MBIs later makes sense. The challenge is part of one epic will be more important than parts of an epic that in turn has more important parts in it. Epics make it difficult to get alignment.