Darkmoon Covenant...in the original Dark Souls. Have fun serving a complete twat. :3
A lot of those people put the hours on PgP (Player griefing Player) though.
The lag can be really atrocious at times. My very first invasion in DSII, I was literally backstabbed from across the room; it's what really happened, this isn't a comedic exaggeration - my character got pulled across the room to be on the receiving end of a backstab. What's worse is that it was a US player (probably with internet running on hamster wheels).
PvP can be fun, depending on how you want to approach it. Judging by your request of assurance by a fighting game player, I take it you are looking for 1x1 duels. There are covenants that specialize on that - the Brotherhood of Blood (it focuses both on invasion and dueling between its members) and the Dragon Remnants (they leave a sign for the player to call and challenge them).
If you have a friend, preferably in the same region, you can easily set up some duels and IMHO that's where the PvP experience shines. There's a item that lets you narrow down servers to make it easier to meet. The only issue is the new Soul Memory system where both players must have to be in a certain threshold of total obtained souls for the matchmaking to work.
I personally recommend the entrance to Cathedral of Blue for dueling, it's a square area large enough to move around but small enough to prevent one player to run off and go ham with spells, but if you want that, the immediate adjacent areas deliver. There is also a bonfire nearby.
The Dragon Remnants are the ideal covenant for this as their summon sign is of unlimited use. The Brotherhood of Blood duels are all done in a specific arena and you have to clear a area and have a item to access it...but the same applies to the Dragon Remnants. Both are tricky to access. Theoretically, you can join the BoB much earlier but it requires using a Cracked Red Eye Orb to invade a player and defeat it so you can earn a Token of Spite.
Alternatively, if you want unfair fights, join the Bell Keepers to be called to defend the area from players that enter it (area enemies will be on your side and you can even have a second player join you) OR if you want the reverse, just dawdle around the Belfry areas and get invaded.
Overall note, if you don't have people to duel with, I recommend disabling inter-regional play because getting jumped by people from across the world and die to a stupid ass lagstab is really obnoxious. I enjoy PvP when the players have similar stats and builds and it becomes a game of footsies and spacing, a little like a 3D Samurai Shodown where things can be decided in a few clean hits. It's also good when you're opponent isn't a dirtbag that never stops circling you in hopes of winning the backstab lottery.
Sorry if I overdid my exposition but I don't know how familiar you are with the game and I get the impression your decision of buying it is hanging on this matter.
I SHIP IT.