Short answer yes, but with MC-AE your attached device MUST be configured and run LACP, as this is required with Juniper MC-LAG implementation.
As for A/A and A/S, A/A config on Juniper MC-LAG means the 2 Core Nodes can run A/A, but can also operate with remote device being A/S if that is they way the device operates, like most FW's. It is almost the same as A/A remote device, that has one link down/disabled. The remote A/S FW makes the Core think one-side is down, so Core knows to only use the one Active link. This type of config is very common, with A/P Server NICs being perfect example. In this situation the Core Nodes are still configured A/A, but only one side actually sees any traffic, the other side is thought to be down. It will be the remote device which will determine which one link to be be active at any specific moment in time. The Core knows both links can be Acive.