Arena supports both group play and 1v1, both are ranked with an ELO-style point system. At the start of each map, you can get a glimpse of the opponent and have a few seconds to change your spec according to their class (or their playstyle if you recognize them with Blade & Soul Gold). Then it’s a duel in an open area with no line of sight obstructions or walls to run up on. There are PvP-specific consumables but you can only use a certain amount(1) each match. You gain PvP currencies and there are also daily quests for participating in arena.
Equalized-Gear in ranked PvP: Gear in arena is supposed to get equalized before end of 2015, so it’ll come for NA eventually.
eSport. As of 2015, CH and KR are the biggest contenders and they have international matches. TW and JP have local tournaments but they are not competing with CH and KR. It’s partly because TW and JP are not on the same patch schedule as the older regions, while CH and KR are very close.
Many PvP players actually love the Mushin Tower even though it’s PvE content. It is a series of solo-only end game instances where you face stronger enemies as you climb the tower. Unlike regular PvE instances, the encounters in Mushin Tower can get very intense and require almost as much timing and reflex as PvP.