To link the PA2 with AE5 you only need a 3-pin cable which already comes with the PA2. AE5 does not come with such a cable.

The PA2 controller has two aquabus connectors. So if you want to add a second PA2 you can connect it to the first controller or you use a y-adapter on the AE5. It does not matter how you connect them since this is a real bus system.

Sensors which are attached to the PA2 controllers are also available for AE5.