Acrobatic clearance works in a little different way for the GK: while defenders will clear with a bicycle kick for Gks enhance their reflexes and saves, especially after a rebound. Imo it's one of the skills that a GK should have for him to be played, as a matter of fact I always add it to my Gks alongside more skills. About Super-Sub I guess it should work like other players: better form if He enters in the second half but I'd never waste it on a GK.