It's my understanding that he was heavily into producing up until 20/20. The failure of
Friends really bummed him out, and it shows: every album up to 20/20 is a cohesive work of art. Even when the other band members contributed you can still hear Brian's touch on the production and flow of the album. But 20/20 is a jumbled mess of songs. No matter how you feel about the album, you can't deny there is a chaotic flow when it comes to production and track listing.
I do believe it was around this time (20/20) that Brian started staying mostly away from the studio, listening from his bedroom above, coming down to suggest things and sing vocals.
As for the production on Smiley Smile: this was definitely Brian's production. Mike Love and Bruce have told stories about Brian really making the guys work hard on the vocals. And who else in that band would empty a swimming pool to record Heroes and Villains in?
