1. By default, every core circle member is entitled to participate in governance meetings. You can change this for multi-filled roles:
2.3.2 Exclusion for Multi-Filled Roles
If multiple Partners are assigned to the same Defined Role in a Circle, the Circle may enact a Policy that limits how many of them are Core Circle Members as a result of that Role assignment. However, the Policy must allow at least one of the Partners filling the Role to represent it as a Core Circle Member, and must specify how that representative will be determined.
2. All partners in a role that controls a domain can access that domain on their own authority. Just as any role in a circle which controls the domain can access that domain. There is no 'making the decision together' - each person gets to decide for themselves.
Hope that helps!
Best wishes, Andrew