From my experience, the only difference between the regular GNW and the Cross-Server GNW are .. First, the background of the interface, Second would be the feature where you can watch battles of the other lands, Third the Rewards Gain from winning/losing a round (Regular only gives 1k group coins while xGNW gives 1.6k group coins), Fourth is the Group Packs and lastly, your opponents will be from other servers so you will have no idea on how they will play the game, and that's where the strategy and instinct will come, and a little side of luck ..

Your group needs to get the first place in your regular GNW against other groups in your server ..