Do these actually provide any additional benefit on country roads or are they just more decoration ?

They are quite useful and not just decorative.

Out of curiousity, how should they be used? Are they like main beam?

Yep, they are the main beam. We'd be lost without them.

They use the same wiring as the 500 i think. So the big lights are dipped beam, and when you put full beam on, it's the smaller pod type lights you mention. With the 500, the smaller lights (also used as DRL's) are main beam, the big lights are just for dipped beam. Seems strange but ah well...