
I would like to create corporate templates (epic, kanban columns, work status, and report/dashboards) within Agile Accelerator so that when a PM installs Agile Accelerator in a client's sandbox/prod instance they can also upload our corporate template VS building it from scratch to mirror our required templates. How could I do this? Unmanaged package(s)?

We did something similar based on a workflow.
You could create a workflow with your company templates built in. It could launch form a button with a short interview to get the team member names and a name for the product.
1. Create a team. Add team members
2. Create a Product tag.
3. Get column settings. I added a reference team with columns assigned to it. That let me loop through the column records (looking for reference team items), and create duplicate column records assigned to the specified team.
4. That is enough to create the Kanban board.
5. Get the default column ID for the new Kanban board and create work items.
6. Create the work items. I added a reference field to work items. That let me get all of the Work records that were reference ones, so I could update the team name and specific Kanban board default column.
At the end, this gives you a default Kanban board based on your specified column settings and a collection of template work items for you to begin with. The user just needs to enter the Product Tag. The team name can be based off the tag with a formula. The initial team members can be the user and 1 other.