[quadplay]

In short, yes - you can use both at the same time! The choice between Composite or RGB is for the SCART connection, and is chosen in the Settings menu. The setup you describe above should be fine as the boxes have an RF output, but new digital STBs don't have an analogue pass-through, so you'll need a separate aerial (or a friendly installer who can split the cable) if you want to record a different analogue channel to the one you're watching on digital.