Does the organization level at which I add someone in the People file affect their access to P&SS?
Yes. If the person is assigned an Administrator role, they will be able to access the organization they are associated with in the People file, and organizations following below them in the hierarchy. If the person is assigned a Contributor role, their level of access is determined by the level at which they are assigned as a Lead in P&SS.
I want to give a user administrator permissions for multiple organizations in the hierarchy. Is this possible?
This is currently not possible. The only option would be to add the user as an administrator and then assign them as a lead to the other organizations.
Does it matter what organization a user is associated with if they are only going to be part of the feedback flow process?
No. Their permissions, roles, and organization affiliation do not matter as long as they are assigned to the programs when the feedback flow is created.