Ok, I was actually at that concert. Brian's actual appearance on stage was brutal. BRUTAL. Physically he looked good, yes. But Landy was using him like a trained Bear. The audience couldn't understand a word he was singing (this was all dubbed in post production) and his strutting? As a Beach Boys and Brian hard-core fan, I was really embarrassed and hard pressed to explain it to the casual fans in my group. They didn't know WHAT was going on.
There's an audience recording of the show floating around somewhere, and I recall that Brian really butchers "In My Car" in particular. What we see/hear on the TV show seems to be a mixture of pre-recorded studio elements, and then some if not most or all of Brian's live vocal replaced with a re-record.
Brian did that little mini solo set at some some shows in 1989. Truly bizarre. They get Brian back for shows, but apart from a few things ("Surfer Girl"), they literally segregate, with the band doing most of their set without Brian, and then Brian doing his set without the band (with some of the backing guys staying on stage).