If people really want to be 100% sure how a group they're interested in sound live, they should simply check on encores, behind the scenes and radio performances
I'd also recommend Sketchbook, but from what I understand, there's some audio upscaling/tweaking/tuning being done at the show as well, to make it sound just that tad better?
Something I've always wondered, even years ago already: if every music show has the groups perform like 4-5+ times for recording, and they're using and knitting several different clips from multiple performances for 1 video broadcast, while using only 1 audiotrack, either from 1 performance or a separate audio - won't you always have moments where video (lip movements) and audio won't sync up?
Because unless I'm mistaken, if they're using different videoclips from different performances, they're not using the audio belonging to each of those clips?
And if a music show simply uses a different, clean audio track not coming from the performances - because it takes less time and effort and it's easier and it sounds so much better to them - then it doesn't matter at all whether a group has sung live, with or without backtrack, at their performances since the audio came from another source anyway?