Can confirm from experience that yes it does apply to all weapon swaps.
as for your second question it kind of depends on your class, but as a generality I find that 2h is much more effective in pvp than dual wield. The most important reason is because it offers a gap closer and a hgh burst damage execute. For dual wield the only truly effective ability for pvp is quick cloak which is basically a perma sprint (but really has little value if you dont have a gap closer).
HOWEVER, for my stam templar, dual wield is superior in PVE. it provides much better synergy with my other skills. Also as a templar i already have a great single target ability in biting jabs that for outweighs wrecking blow (2hs main dmg ability). and gap closers arent as significant in pve as they are in pvp.