You face a choice between the best lounge or the car/van transfer on the way back.

For the outbound it is easy, go to the FCL A and get a transfer to the E lounge. While you are at A, check out the lounge.

On the inbound, you can take the transfer to A straight from the plane, this will cause you to miss the FCL E, but also the train and passport control queue as you can use the booth at the bottom of A, like on the outbound. You spend the rest of the time in the FCL E.

Alterntively, you walk from the plane to the FCL at E, spend up to 3 hours there, then go through passport control and take the train to A to your connecting flight, Or leave earlier and spend another 30 min in the FCL A.

The FCL E is nicer and has a terrace but the FCL A also has showers and a decent breakfast.