WP's are instanced to a a 1v1 WPvWP scenario (as far as I know)
Similar to the RBG system in WoW, there will be individual ratings as well as a WP rating. This is my current understanding of the match making system, but of course it's only a good practice if there are a lot of people participating.If that's the case I wonder how they will try match up both War parties to make sure it isn't totally one sided, It might take into account the PvP rating each member in you team has and come out with an average.
Warplot battles can only occur once the owner of the Warplot agrees to the battle. These battles can bet entered through a Matchmaking system. Since Warplots are pieces of floating land, once a battle is agreed upon, the Warplot can move near the challenged party's Warplot to face off. The victor of this battle will receive rewards based on their victory, and the loser will be forced to rebuild because their Warplot will be destroyed.