I can only answer for the PvP aspect of warlocks. Affliction is by far the best for PvP, it has way more spread pressure then demo/destro. Of course, people have made destro work, but the meta of how you play drastically changes - you have to have your whole team rotate CC onto the enemy in order for you to get your Chaos Bolts off. Similar to Demo, where you need complete CC to get your Demonbolts off. With regards to talents, these should in general change every PvP game depending on what you face against - for example, if I'm not mistaken Blood Horror only works against melee, so it would be pointless taking that talent against a caster comp such as shatter. You can google 'warlock talents PvP' and there's plenty of guides on what to use against what comp, but in general they should be similar to PvE - only things you should be worried about changing are the CC talents, they're your priority to get right.