[Nicky91]

uh characters don't really say anything who is behind them tbh

no need to speculate now either, no use you can speculate during first show (when you get hints for first time)

but the celebs their voices are masked too so you won't hear their real voice with the hints

during the singing they don't lip sync, they got a mic near their mouth, that is where they are singing through, the microphone in their hand is just for the overall look of a performance