There are two forms of PvP in Elements -- Random and Duel. Random will pit you against another player looking for a challenge. In this mode the winner gets some electrum (the currency of Elements) depending on the scores of the players before the match and three spins on the wheels. As usual the wheels may reward you with a copy of any card from your opponent's deck. Note that you cannot win upgraded cards from PvP spins -- if your opponent carries them, only the unupgraded version will be made available through spins.
In Duel mode you and another player have a friendly match. You may choose who you play and if they accept you will begin a normal game. The exception is you will not win chances to spin the wheels or score. However, sometimes you will be awarded up to 20+ electrum.
PvP can be rewarding in terms of score and electrum gained especially when one wins in a matchup against a higher rated player. Generally however, PvP is not used for grinding because of the superiority of human intelligence in understanding and applying strategies as opposed to artificial intelligence (AI). T50 decks vary less in terms of strategy and contain more rares although similarly, only unupgraded cards can be won.
PvP Tournaments are held on weekends in the Elements chatrooms. The format is single elimination and deckbuilding rules change from week to week to encourage variety. Prizes include Electrum for the top 4, and first place gets to choose any card in the game including Nymphs and the exclusive Mark cards. If you’re interested in participating check here: