When I run a test configuration with several physical devices on the Robo Test Lab (from either the firebase console or by uploading the app to the play store), do the devices run in parallel or serially?
My robo setup script will not be 100% reproduceable if the devices are running in parallel due to sharing the same setup parameters among the test devices, so I could use knowing if I must put code in place to handle this.
Devices are acquired and tests executed as quickly as possible, i.e. most of the time your tests will run in parallel on different devices at the same time.
There's no way to configure the tests to be serialized. You would need to do this yourself, by starting a test on one device and wait for it to complete before starting another one.