What drives the scheduling for Portfolio for Jira?

[Danny Davidson]

I am trying to put together a road map of work for Q4 2019 and Q1 2020, and I am having the most difficult time understanding what is driving the scheduling of tasks. 1 thing I have figured out is, that by adding a release date to a fixed version, issues in that version get scheduled within that time frame. But here is what I would like to know...

What about issues that are not in a fixed version?  For example, if I have an Epic that is not part of a fixed version, it has 10 stories that add up to 50pts.....how do I manage something like that? How is start date and end date determined for the epic?.....same for the underlying stories? I assumed due date would be the primary factor, but that doesn't seem to have any effect. Also, what if the work is still in my backlog (i.e. not in a created, future sprint)? 

Also...Im using v2.16 I believe...but its definitely not the newer interface.