You do not need to play PvP at all, it's entirely optional.

as far as solo goes, it's very much like any other mmo - certain quests - often optional req groups, dungeons req groups but the main quests - and quests in general does not require any groups. You can absolutly get throuhg it to lvl 50 without having to group up even once -.though it will be slower, and your gear will suffer somewhat from it.