Answer: There is no global option to send all traffic logs to panorama. Each individual policy will have to be set to send logs to Panorama.
Answer: Users logging into Panorama will only see the device context for which they have access.
Answer: Yes both Panorama and the device will have the traffic logs.
Answer: At the bottom of the device display, choose "display by device-group". The commit will then make changes to all the devices in the group.