As above, so below: can a soul warden with quick channel use channel casting as a move action, or is the casting time based on the spell (i.e. just using a channel as a spell slot)? If yes, would it cost 2 uses of channel?
No. Channel Casting is a supernatural ability, and Su abilities use a standard action unless otherwise specified. It expends a use of Channel Energy, but you're not actually channeling, so Quick Channel does not apply to it.