I would like to understand how the L4S feature works with videocalls, specially with FaceTime, since it has been improved and made compatible with this capability. Even if it's just a qualitative comparison, I'd like to compare a video call under network congestion conditions between an iPhone with L4S enabled and one without (on a network that supports L4S). To do this: I would like to know if I could conduct this test using a single device with L4S enabled (in developer mode) and another without L4S, with the server located on the internet. Or both devices would need to have L4S enabled, because the client and server for L4S would then be the two devices themselves (point-to-point). Thank you.